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This will be no easy meeting for German Chancellor Merkel. Disagreement on several issues hangs in the air, while the sideline meetings of Trump, Putin and Co. could overshadow the summit itself, Bernd Riegert reports.
Police have diverted traffic in the center of the north German city of Hamburg the night before the start of the G20 summit, meaning pedestrians and cyclists can move around on the four-lane main roads freely.
"In the city center it's actually a lot quieter than normal," says restaurant owner Nico in the central district of St. Georg.
But in the Hamburg areas of Schanzenviertel, Sankt Pauli and Altona, which are close to the convention centre where the G20 summit is taking place, there is a different atmosphere - in fact things are, at times, violent.
On Thursday evening, police broke up a demonstration at which 1,000 members of the "Black Block" - the extreme anarchist end of the anti-capitalist movement - had gathered. According to authorities, around 6,000 protesters were still moving around in groups overnight. At least 76 police officers were injured in the various scuffles.
While other demonstrations taking place in Hamburg, involving anything from "anti-G20 yoga" to "dancers against the summit," remained peaceful, some residents are still uneasy. Many shops in the center of the city are boarded up with wood or metal to protect against violent demonstrations.
A local newspaper said that three-quarters of all Hamburg residents are against the hosting of the G20 in their city, although schoolchildren may be of another opinion as they have been given Friday off from classes.
Lack of consensus on climate issues
The two-day meeting between the 19 most important industrial and emerging economies in the world (plus the European Union) will begin with a discussion on the fight against global warming. US President Donald Trump and Russian President Vladimir Putin will not take part in that, however, and have scheduled a formal meeting with each other instead.
Trump's absence from the climate discussion shows German organizers that the United States would prefer to leave the issue out of the all-important summit declaration completely.
German Chancellor Angela Merkel suggested on Thursday evening that officials would have two long nights ahead of them as they attempt to settle on a declaration wording that all parties can agree on. "The negotiations are not easy,” she said.
Currently many contradictions still exist between the participating nations, not only on climate change policy, but also on world trade and migration. Some summit diplomats have said that the US could oppose the rest of the G20 membership and abandon the goal of reaching a general consensus altogether.
The summits within the summit
As summit chair, Angela Merkel has tried in recent days to speak to almost all important G20 participants, to make them aware of the parameters of the meeting. But the upcoming G20 conference, the tenth of its kind, is overshadowed by a number of international crises in a world which Merkel describes as "in turmoil.”
According to the US, the most important issues lie outside the G20 meeting agenda, which include financial policy, the economic structure of the world's digitalization, investment programs in Africa and more rights for women.
Instead, Trump plans to focus his energies on meetings with both the Russian and Chinese presidents. The US president criticized both men sharply ahead of his trip to Hamburg.
Russia was playing a "destabilizing role,” Trump said during a speech Thursday in Poland, although it was unclear whether he was talking about the country's dealings with Ukraine or its hacking attacks on the 2016 US presidential election.
Domestically, Trump is under pressure, due to official investigations into possible connections between his campaign team and Russian officials and the promised improvement in relations to Russia have not yet appeared.
Last week national security adviser H.R. McMaster said that Trump had prepared no specific agenda for the meeting with Putin. "It's whatever the president wants to talk about,” McMaster told reporters.
Three-way meeting on Ukraine
One of the topics that Trump is likely to touch on with the Russian president is the Kremlin's role in the conflict in Ukraine. Merkel wants to meet French President Emmanuel Macron and Putin about the situation in the east of the country and the peace process there.
It's unclear what can actually be expected to come out of this, likely short, conversation. So far, the rebels in eastern Ukraine, who are apparently being directed by Russia, have not abided by the points drawn up in the Minsk Protocol. Russia, for its part, accuses Ukraine of increasing attacks in the region too.
North Korea's nuclear warheads
Trump also plans to talk with Chinese President Xi Jinping about the North Korea situation, at a meeting of Asian G20 members. He has accused China of not doing enough to put pressure on North Korea's Kim Jong Un, who provocatively launched an intercontinental ballistic missile this week, just before the start of the summit.
The US president has said many times that the tests must not continue and that a nuclear threat from North Korea is not acceptable.
Russia, on the other hand, has warned Trump's administration not to use military force in North Korea. Trump and Putin are also likely to discuss the issue, if the US president feels he wants to on the day, of course.
Qatar boycott and trade issues
Another topic which will no doubt pop up at the G20 summit over the next two days is the diplomatic boycott of Qatar, plus the related issue of global terrorism.
Saudi Arabia recently led a bloc of Arab countries who severed diplomatic ties and otherwise distanced themselves from the small emirate. Turkey, who will be represented by Recep Tayyip Erdogan in Hamburg, supports Qatar, while Donald Trump is expected to make a clear statement at the summit on the boycott, too.
The Saudis cite Qatar's supposed links to terrorism as the reason for their boycott, but the move is sure to come under some scrutiny. After all, the definition of terrorism for Saudi Arabia, Turkey and the European Union appears to encompass very different meanings.
Keeping global trade open
As summit chair, Merkel will certainly be called upon to use her diplomacy skills over the next few days. She has said in advance that she doesn't want a meaningless, soft summit communique at any price.
Thankfully, Donald Trump has said that he is determined make the 300-million-euro ($342-million) summit a success. Around 20,000 police are also on hand to make sure demonstrations take place without a glitch and that there are no other security issues.
It all bodes for a fascinating few days, even if the G20 doesn't have an official remit to decide on worldwide issues and is more of a working group.
Over the last few days, Hamburg's world famous harbor has been home to a large banner hung on the side of a shipyard, with a surprising protest message. It reads, "Keep global trade open!” - an unfamiliar catchcry of G20 protesters.
Trump, with his "America First" motto, may have something to say about that motto too.