The G7 summit began with a sense of impending doom and included a twist in the form of a surprise guest, but ended with smiles and a delicate breakthrough — President Trump may now be on course to meet with Iranian President Hassan Rouhani.

Driving the news: French President Emmanuel Macron, the host, revealed during a joint press conference with Trump today that he has been working to broker such a meeting. That explained his decision to invite Iranian Foreign Minister Mohammad Javad Zarif to Biarritz, a move that raised eyebrows around the world yesterday.

The big picture: Trump has long wanted to meet Rouhani, but Iranian officials have rejected the idea on grounds that the U.S. is waging "economic warfare" against them.

Macron said he told Zarif yesterday that a deal can be made if Iran agrees to a meeting. He touted Rouhani’s statement today that he would be willing to meet with an “individual" if it was in Iran’s interest.

Macron said the idea to invite Zarif came after Saturday's dinner with the other leaders, and he added that he informed — but did not ask — Trump before issuing the invitation.

Flashback: Trump unilaterally withdrew from the 2015 Iran nuclear deal last May, calling it the worst deal in history. Macron has led the remaining signatories in attempting to salvage the deal.

Iran's patience is growing thin amid suffocating U.S. sanctions, and it has begun to creep outside the deal's obligations.

Macron has clashed vigorously with Trump on the issue, but was conciliatory today. He said he and Trump share the same objectives — to prevent Iran from obtaining a nuclear weapon and to avoid further escalation in the Gulf.

There are obstacles to a meeting on both sides, though.

Rouhani answers to Iranian Supreme Leader Ayatollah Ali Khamenei, who has previously ruled out negotiations with the U.S.

Trump’s administration is stocked with Iran hawks who are more wary than the president of breaking from the “maximum pressure” approach.

But Trump was relatively concrete in terms of what was on the table.

He said he's not seeking regime change in Tehran, but instead wants a longer-term nuclear deal that includes increased surveillance and also covers ballistic missiles.

Trump said he’d be willing to offer a “letter of credit,” sourced from "numerous countries" and backed by oil, to help relieve Iran’s short-term crunch. In the meantime, he said, “they have to be good players" or risk "very violent force."

Macron sounded bullish, saying he hoped the meeting would take place within weeks and ultimately lead to a new nuclear deal.

What to watch: Macron dismounted the diplomatic tightrope with a hug and warm words from Trump. Afterward, Trump tweeted a video captioned: "THANK YOU FRANCE!"

It's a stark contrast with a year ago, when Trump lambasted Canada's Justin Trudeau as "dishonest and weak" upon exiting the G7.

We're a long way from a new Iran deal, though, and Macron knows from his history with Trump how ephemeral moments like this can be.

Other summit highlights

Trump claimed Russia was expelled from the G8 because “President Putin outsmarted President Obama,” blaming his predecessor for Russia’s invasion of Crimea and reiterating that he’d like to see Putin back at the table.

Trump was conspicuously absent from a meeting on climate change. He also continued to promote his property in Doral, Florida as the ideal venue for next year’s gathering, despite concerns that he'd personally profit from its selection.

Trump announced a trade deal "in principle" with Japan. The details could be ironed out by next month.

He praised Chinese President Xi Jinping as a "great leader" who wants a deal and will ultimately get one. Days earlier, he'd called Xi an "enemy" and said the U.S. would be "better off without" China.

The big picture: Macron was wise to rule out a joint statement in advance. The leaders didn’t collectively agree to much other than a fairly paltry sum to fight fires in the Amazon.

The bottom line: “It’s hard to think of a topic the US isn’t allergic to or doesn’t push back on now,” a senior European diplomat told the FT. “Or if there is agreement between the participants, it’s the lowest common denominator — at the level of ‘the sun rises and the sun sets.’”

Go deeper: Israel alarmed by possible U.S.-Iran talks.