By Laurence Norman, Wall Street Journal: The plan, aimed at reducing tension between Washington and Tehran, was outlined by French President Emmanuel Macron in discussions with President Trump last week at the Group of Seven leaders’ meeting in Biarritz, France.

Mr. Trump’s commitment remains uncertain to a deal that would let Iran export more oil and draw on an international line of credit. And the Iranians could scupper momentum for any deal by further breaching the limits on their nuclear work set out in the 2015 accord. On Friday, an Iranian tanker was set to offload crude onto ships that would take it to Syria, breaching terms of its release following its seizure by Gibraltar in June on suspicion of transporting crude to Syria in violation of U.S. sanctions, The Wall Street Journal reported Friday.

Iran’s Foreign Minister Javad Zarif has called the French proposal “productive,” and Iranian officials are expected in France in coming days to continue work on it.

Neither the White House nor the State Department responded to requests for comment on Friday.

While Mr. Trump indicated receptiveness to Mr. Macron’s idea following the G-7 summit, top administration officials including national security adviser John Bolton have cast doubt on the idea of easing any sanctions in the absence of a comprehensive deal.

A senior Trump administration official said the Europeans “are desperate to salvage a terrible deal.”

“The president has been clear: Iran isn’t going to receive tangible economic benefits from the United States for reverting back to a completely inadequate agreement,” the official said.

The French initiative, European diplomats say, would represent the first real prospect of dialing back hostilities following a series of attacks and ship seizures in the Persian Gulf that have brought Iran to the edge of conflict with the U.S. and its allies.

“We are all of the view that the momentum that may be there…has to be seized,” German Foreign Minister Heiko Maas said Friday after being briefed on the talks by his French counterpart.

European officials, in urging caution, said Mr. Trump was often unpredictable and faces pressure from some advisers and U.S. regional allies opposed to relaxing the administration’s stance on Iran.

In a phone call on Friday, Israeli Prime Minister Benjamin Netanyahu urged Mr. Macron not to pursue talks with Tehran now, his office said.

Israel has sought to target what it perceives as Iranian threats in the region and has recently widened that campaign beyond Syria to include strikes on Tehran’s allies in Iraq and Lebanon.

“This is precisely the wrong timing to hold talks with Iran,” Mr. Netanyahu said.

At the G-7 meeting in Biarritz, Mr. Macron pressed Mr. Trump to consider steps to allow Iran to boost oil exports to help its badly weakened economy, officials briefed on the talks said.

As part of the lobbying push, Mr. Macron invited Mr. Zarif to the seaside town for separate talks on the summit’s sidelines.

European officials say conditions could now be coalescing around a preliminary agreement aimed at allowing Iran to be able to sell at least 700,000 barrels of oil a day—more than double its current exports.

It also envisions a credit line of some $15 billion so Iran could draw on hard currency, getting around U.S. sanctions that freeze Iran’s export revenues in foreign bank accounts.

Messrs. Macron and Trump discussed the French initiative at a meeting that U.S. Treasury Secretary Steven Mnuchin and French Finance Minister Bruno Le Maire joined, according to several diplomats briefed on the discussions. Mr. Trump said he was open to the idea and told Mr. Mnuchin to follow up with Mr. Le Maire, these diplomats said.

Mr. Trump told reporters on Monday that Iran may need a “short-term letter of credit or loan…to get them over a very rough patch.”

On Friday in the Finnish capital, French Foreign Minister Jean-Yves Le Drian briefed his European counterparts on the talks.

He said it wasn’t yet clear that the U.S. would forgo sanctions on additional Iranian oil exports but that there had been no signal from the White House that Mr. Trump would block the initiative.

On Friday, the United Nations atomic agency confirmed Iran’s stockpile of enriched uranium remained well above the 2015 agreement’s 300 kilogram limit and Tehran was still enriching uranium to 4.5% purity, above the agreement’s 3.67% limit.

The larger Iran’s stockpile of enriched uranium becomes, the less time it would take for it to amass enough fuel for a nuclear weapon.

Tensions have flared in the Strait of Hormuz, where Washington blames Iran for planting mines on commercial tankers. In June, the U.S. prepared to launch a retaliatory strike against Iran after it shot an American reconnaissance drone, but the mission was called off at the last minute, U.S. officials said.

Animosity between Washington and Tehran soared after the U.S. exited the landmark nuclear agreement in May 2018 and reimposed sanctions on Iran’s hobbled economy.

The deal’s other participants—France, the U.K., Germany, Russia and China—have pledged to uphold it.

For months, Mr. Macron has attempted to bring the different sides together. He has sent his top diplomatic aide to Tehran and explored ways with his U.S. and Iranian counterparts to prevent a conflict.

European officials have warned of a potential mismatch in expectations between Iran and the U.S. over what a preliminary deal might contain. Washington potentially would expect Iran to do more than hold to 2015 nuclear deal’s terms and agree to concessions in other areas, such as curtailing ballistic-missile tests.

European officials also say they believe Iran has grown more confident in recent months. Mr. Trump not only called off the planned attack after Iran downed the U.S. drone, but has also appeared more eager for talks and seemed to narrow his demands on Iran to denying them any future path to a nuclear weapon.

Iran’s President Hassan Rouhani this week walked back comments suggesting he was open to meeting with Mr. Trump, and senior officials in Tehran said the U.S. must lift sanctions before Iran would agree to talks.

First published in Wall Street Journal. Cartoon by Amjad Rasmi.

—Benoit Faucon in London and Courtney McBride and Vivian Salama in Washington contributed to this article.