Leaders of 27 EU countries have unanimously backed the Brexit deal. The UK's parliament will vote to ratify the deal in a rare Saturday session. Follow the developments as they happened.
Read a summary of the day's Brexit events here: EU 'sorry' to see UK leave as leaders agree to Brexit deal.
Read the events of October 17 as they happened below:
All updates in Universal Coordinated Time (UTC)
17:51 German Chancellor Angela Merkel said the EU and the UK need to wrap up a free trade agreement as soon as possible following the UK's exit from the bloc. She told a news conference that the Brexit deal facilitated an orderly Brexit and a transition period until the end of 2020, giving time for such an agreement to be settled.
"There is an essential difference compared with when Theresa May was prime minister. Then it was not clear how future relations would look, whether there would be membership of the customs union or not," Merkel said. "Now it is quite clear that Great Britain will be a third country and with this third country we must sort out a free trade agreement very quickly," she continued.
17:40 President-elect of the European Commission Ursula von der Leyen told reporters that the deal was of utmost importance "as a starting point for future relationship to the United Kingdom." "On the other hand, of course I'm sad that our British friends are leaving the European Union," she said.
17:05 In his own press conference following the EU's endorsement of the Brexit deal, Johnson said there was "a very good case for voting for this deal" on all sides of the House following negotiations he called long, painful and divisive. "I'm very confident that when MPs of all parties look at this deal they'll see the merits of supporting it, of getting Brexit done on October 31, and of honoring the promises made repeatedly to get Brexit done," he said.
Brexit Secretary Stephen Barclay, Prime Minister Boris Johnson, Jean-Claude Juncker, President of the European Commission, and Michel Barnier, the EU's Chief Brexit Negotiator, ahead of the opening sessions of the European Council summit at EU headquarters in Brussels.
16:42 In a press conference following the endorsement, President of the European Council Donald Tusk said that if there's a request for an extension made, he will consult member states on how to react. He also said that the EU and the UK were "very close to the final stretch" of Brexit, with approval of the British parliament and the European Parliament as the last hurdles to surmount. He also expressed sadness at the prospect of the UK leaving the EU, saying he's "always been a Remainer."
EU Brexit chief negotiator Michel Barnier said the UK would remain "our economic partner, our friend and our ally" to guarantee Europe's security, and that the future relationship the EU and the UK negotiate in the next phase of Brexit would prove more important than this accord.
16:39 German Chancellor Angela Merkel said that achieving the deal had been "real hard work," and called the agreement "a compromise for all sides," and "an opportunity to have good, close relations with Britain in future as well." When asked whether the EU's apparent refusal to consider an extension undermines the UK's parliament, she said: "We will address any decision by the British Parliament and didn't make any decision today for any eventuality."
16:10 Leaders of the remaining 27 EU countries have unanimously endorsed the Brexit deal, formally sending it to the UK's parliament for ratification. The leaders invited EU institutions to take steps to ensure the agreement can be implemented on November 1, but emphasized they wanted "as close as possible a partnership with the United Kingdom in the future."
15:32 UK Prime Minister Boris Johnson told EU leaders at the summit in Brussels that he was relatively positive about the new Brexit deal passing the House of Commons, an EU official said. Johnson proceeded to leave the room and the 27 EU leaders to debate the matter without him.
15:11 Ahead of the EU summit in Brussels, Johnson was greeted by other EU leaders with handshakes and claps on the back. European Parliament President David Sassoli said the assembly could ratify the draft Brexit agreement by the deadline at the end of the month if it's endorsed by EU leaders and the UK parliament.
"We're ready to do our duty, which is to examine the text and adopt the necessary procedures so that the time limits are respected," Sassoli said. The EU assembly has "the final word, if you like, but the second to last word is in the hands of others," he continued.
EU leaders appear ready to endorse the agreement by Friday, leaving it to the UK's parliament to debate the text on Saturday. If it's approved by both the EU and the UK, the European Parliament could rubber stamp the deal in Strasbourg, France, next week — roughly one week before the UK's October 31 deadline.
13:25 The UK's parliament has voted to hold a rare Saturday session in order to put the Brexit deal to a vote, the first such session since the 1982 Falklands War.
Parliament will sit from 08:30 UTC on Saturday, at which time Johnson is set to make a statement to lawmakers, followed by a 90-minute debate and then voting. The vote is one necessary step to ratify the deal. If the deal passes through parliament, legislation would then need to be passed by the October 31 deadline to complete the ratification.
Johnson's new plan faces significant opposition in a deeply divided parliament, with his rivals — among them Labour leader Jeremy Corbyn, Scottish First Minister Nicola Sturgeon and Brexit party leader Nigel Farage — rejecting the new plan immediately after it was announced.
13:10 European Commission President Jean-Claude Juncker reiterated to reporters in Brussels ahead of the EU summit that he has ruled out granting the UK another Brexit extension. "There will be no prolongation," Juncker said. "We have concluded a deal so there is not an argument for a further delay." Johnson said that the deal allows the UK to leave the EU "in two weeks' time" in a tweet earlier today.
This could raise the stakes in the House of Commons when it votes on the proposed deal. It's designed to leave those parliamentarians reluctant to accept the deal as agreed by Johnson thinking that their choice is between this deal, and none at all, at the end of the month. However, this decision is not Juncker's to make, but that of the leaders of the other 27 EU member states.
At a press conference with Johnson earlier today, Juncker said he was "happy about the deal and sad about Brexit."
Speaking alongside Juncker, British Prime Minister Boris Johnson said the agreement was "a very good deal for both the EU and for the UK," and that the deal would allow the UK to leave the block as scheduled on October 31 "whole and entire."
12:56 After reaching a five-month high of $1.2941 following Thursday's announcement of a Brexit deal, the British pound was trading 0.3% lower at $1.2789 after Northern Ireland's Democratic Unionist Party (DUP) said it could not support the plan, adding that it was "not in Northern Ireland's long term interests."
12:50 British lawmakers have approved the government's plan to vote on Prime Minister Boris Johnson's Brexit deal during a special session of parliament on Saturday. They also backed a change to the rules that would allow amendments to be proposed and put to a vote.
The prime minister has urged MPs to "get this excellent deal over the line."
12:44 Irish Prime Minister Leo Varadkar says the Brexit deal is good for Ireland and Northern Ireland, hailing the avoidance of a "hard border."
"We have (a) #Brexit Agreement that allows (the) UK (to) leave (the) EU in (an) orderly way," Varadkar wrote on Twitter. "We have (a) unique solution for NI that respects (its) unique history and geography."
12:33 Leader of the British House of Commons Jacob Rees-Mogg says a 90-minute debate on the Brexit agreement is expected to take place in the UK parliament on Saturday. British lawmakers are due to vote later on Thursday on whether that weekend session should go ahead.
"The prime minister will make a statement updating the House on the outcome of the negotiations at the European Union Council. The debate that follows will be a motion to either approve a deal or to approve a no-deal exit," Rees-Mogg said.
Read more: What's new in this Brexit deal?
12:06 DW correspondent in Brussels Georg Matthes says concessions have been made on both sides, notably, on the UK's side, that Northern Ireland will remain aligned to the standards of the internal market and the customs union. "If you look at the EU side, the main concession here really is that it will be UK customs officials who will be controlling that the EU's customs laws will be applied when it comes to goods crossing from the UK into Northern Ireland," he said.
11:47 German Foreign Minister Heiko Maas has described the agreement as "nothing less than a diplomatic feat."
He told reporters in Berlin the deal was "proof that we all worked very responsibly together," but stressed that it still needed to be discussed by EU leaders and the European Parliament.
11:39 Nicola Sturgeon, the leader of the Scottish National Party (SNP), says her party rejects the new Brexit deal because it "would take Scotland out of the European Union, out of the single market and out of the customs union against the overwhelming democratic will of the people of Scotland."
She said lawmakers with the SNP, which has 35 seats in the 650-seat House of Commons, "will not vote for Brexit in any form."
11:23 Irish Foreign Minister Simon Coveney says the deal is "a big step forward" and worth supporting because it protects Irish interests.
"It's a deal that recognizes all of the issues that we have been raising for the last three years. It is a deal that will protect people on this island, it will protect peace on this island, it will protect trade on this island," he said.
11:14 Brexit Party leader Nigel Farage is calling on the British Parliament to oppose the new deal, saying it's "just not Brexit" and still binds Britain to the EU. He said he would prefer to see a "clean break" with Europe rather than "another European treaty."
He added that he also favors new elections and an extension of the October 31 Brexit deadline over a parliamentary vote on the current terms.
11:06 The EU's chief Brexit negotiator, Michel Barnier, says Northern Ireland will remain in a customs union with Britain under the agreement, but will continue to apply limited EU internal market rules in order to avoid border controls with EU member Ireland.
Barnier said a dual customs regime would be observed, depending on whether goods are destined to stay in Northern Ireland or end up in the EU.
He added that the EU and the UK wanted to negotiate a free trade agreement, and that Brussels was offering a deal "without tariffs and quotas between the EU and the UK."
10:57 In his initial response, Barnier hailed the deal, saying it answered the uncertainty created by Brexit: "We have delivered, and we have delivered together."
The agreement still needs to be ratified by EU member states and UK lawmakers. Barnier said that Johnson "told President Juncker ... he believed he was able to get the deal approved," by British MPs, adding that Johnson said he was "confident about his capacity to convince a majority."
Read more: Merkel: Brexit deal 'better for everyone'
The House of Commons on three occasions rejected previous Brexit agreements under Johnson's predecessor Theresa May.
10:49 EU Commission President Jean-Claude Juncker has urged the 27 member states to get behind the Brexit deal. In a letter to EU Council President Donald Tusk, Juncker said EU countries are "best served by an orderly and amicable withdrawal of the United Kingdom from our Union."
"Our hand should always remain outstretched as the United Kingdom will remain a key partner," he wrote.
"I believe it is high time to complete the withdrawal process and move on as swiftly as possible to the negotiation on the European Union's future partnership with the United Kingdom."
10:45 Finnish Prime Minister Antti Rinne said: "The ball again is in the British Parliament('s court) ... I hope it goes through this time."
"I hope we are now at the end of this process. But there are still many doubts — for instance, inside the British Parliament."
10:41 EU leaders arriving in the Belgian capital for a summit are commenting on the agreement. French President Emmanuel Macron said the deal was "good news."
"The deal now needs to be technically explained, politically presented. It will be done in the coming hours. As far as I'm concerned, I am satisfied we managed to find it and reasonably confident it can be ratified by the British and European parliament."
10:25 Britain's main opposition party is "unhappy" with the new Brexit deal, Labour leader Jeremy Corbyn said in Brussels.
"From what we know, it seems the prime minister has negotiated an even worse deal than Theresa May's, which was overwhelmingly rejected," Corbyn said.
10:14 Dutch Prime Minister Mark Rutte said: "Very encouraging news that there is an agreement, now we have to study the details. But in itself very encouraging."
9:50 The pound has surged following news of the provisional deal on Brexit. The currency, which has been volatile over the past week on conflicting reports of progress, jumped to $1.2934 (€1.16) from $1.2805 earlier in the morning.
9:35 Johnson has praised the deal between Britain and the EU, saying they have agreed on a "great" new Brexit deal and urging lawmakers to approve it on the weekend.
"Now parliament should get Brexit done on Saturday so we can move on to other priorities like the cost of living, the NHS, violent crime and our environment."
9:34 "Where there is a will, there is a #deal — we have one! It’s a fair and balanced agreement for the EU and the UK and it is testament to our commitment to find solutions," Juncker wrote on Twitter.
8:35 The Democratic Unionist Party (DUP) of Northern Ireland has said it cannot back the terms of the current deal on the table.
"As things stand, we could not support what is being suggested on customs and consent issues and there is a lack of clarity on VAT," the party leadership said in a statement posted on Twitter.
7:30 German Chancellor Angela Merkel addressed the German Bundestag and said that an "agreement is still possible," which is, "why we need to continue to do everything to bring the negotiations to a successful end."
law, mmc/rt (AP, Reuters, AFP, dpa)