UK Foreign Secretary Jeremy Hunt told his Iranian counterpart, Mohammad Javad Zarif, on Saturday that London would facilitate the release of the oil tanker, Grace 1, if Tehran assured that it would not head to Syria.
Hunt said he had a "constructive call" with Zarif, and that the Iranian foreign minister had assured him that Tehran "is not seeking to escalate" tensions between the two countries.
"I reassured him our concern was destination not origin of the oil on Grace One & that UK would facilitate release if we received guarantees that it would not be going to Syria, following due process in (Gibraltar) courts," Hunt wrote on Twitter.
Iran's foreign ministry issued a statement on Saturday saying Iran would continue oil exports under any conditions. Zarif had told Hunt this during the call on Saturday, the ministry said.
Zarif also said that Britain should quickly release the tanker.
Last week, British Royal Marines seized the tanker off the coast of the British Mediterranean territory of Gibraltar on suspicion of violating EU sanctions against Syria. The tanker was carrying 2.1 million barrels of light crude oil, the head of Gibraltar's government said.
Iran has denied that the tanker was taking oil to Syria in violation of EU sanctions and blamed the United States for arranging the seizure of the tanker. Tehran has also demanded the UK release the ship, and threatened retribution.
The tanker's interception has strained UK-Iran ties. The British navy said on Thursday it had stopped three Iranian paramilitary vessels from disrupting the passage of a British oil tanker through the Strait of Hormuz, a critical shipping lane at the mouth of the Persian Gulf. Iran's Revolutionary Guard denied any incident had occurred in the strait.
In the wake of the recent developments, the UK said on Friday it was moving up its timetable for relieving the HMS Montrose, a frigate operating in the Persian Gulf, with the larger HMS Duncan destroyer.
The tanker's interception came at a time when tensions in the Middle East are already running high, as US President Donald Trump's administration continues its campaign of maximum pressure on Iran.
Trump has unilaterally imposed crippling economic sanctions against Iran with the aim of halting Iranian oil exports.
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European countries have not imposed sanctions against Iran, but have had them in place against Iran's ally Syria since 2011.
Gibraltar's police said on Friday that four crew members who had been arrested, including the vessel's captain and chief officer, had been released on bail without charge, but their investigation was ongoing.
Meanwhile, to calm Middle East tensions, the European Union says it supports an Iraqi proposal to hold a regional conference.
During a visit to Baghdad on Saturday, EU foreign policy chief Federica Mogherini warned against "dangerous adventures" in the region. She said the EU's priority was to avoid escalation and any miscalculations that could lead to "dangerous consequences" for Iraq and beyond.
sri/jm (Reuters, AFP, AP)