PARIS (BLOOMBERG) - French President Emmanuel Macron's trip to Russia this week once threatened to split France from its European allies.

Now it's part of a wider European effort to tie President Vladimir Putin to the Iran nuclear accord.

Mr Macron will hold direct talks with Mr Putin on Thursday (May 24) about Iran, Syria, and Ukraine, and on Friday, he attends the St Petersburg Economic Forum, the Russian leader's annual investment showcase.

It's a less controversial trip than it looked in March, when the UK accused the Kremlin of organising a nerve-gas attack against a former Russian double agent in southern England.

Since then, concerns about the alleged Russian assassination attempt have been overtaken by the US decision to quit the Iran deal.

France and its European allies need Russia's help to salvage the agreement and German Chancellor Angela Merkel held talks with Mr Putin in Sochi, Russia, last week.

On Monday, Secretary of State Mike Pompeo set out a list of demands that Iran dismissed out of hand and warned European companies to expect no concessions from the newly reinstated sanctions regime.

"The context for the trip has changed," said Ms Tatiana Kastoueva-Jean, head of the Russia centre at the French Institute for Foreign Relations.

"The Iran accord provides an opening to Russia now that France suddenly finds itself on the same side as Russia and Iran."

Mr Macron defended his decision to maintain his Russia trip - even as he joined other Western allies in expelling Russian diplomats in April - on the grounds that his foreign policy involves keeping communications open with all world leaders, whether it's Mr Putin, US President Donald Trump, or Iran's Hassan Rouhani.

"If France wants to be respected, it must talk to everyone but also be capable of acting when red lines are crossed," Mr Macron said in a May 6 interview with Le Journal du Dimanche.

"I want a strategic and historic dialogue with Vladimir Putin to tie Russia to Europe and not let it turn in on itself."

Mr Macron has never held back from criticising Russia or Mr Putin on election meddling, gay rights, support for President Bashar al-Assad in Syria, or for meddling in eastern Ukraine.

Kremlin officials say Mr Putin appreciates Mr Macron's direct style of talking.

"Each side is looking to maintain this difficult dialogue," said Mr Michel Duclos, a former French ambassador to Syria who now advises the Insitut Montaigne policy centre.

"Putin has been isolated in Europe, while after Trump's decision on Iran, Macron wants to relaunch initiatives in the Middle East."

On Iran, both sides have said they are committed to maintaining the accord limiting Iran's nuclear activities, even if the US has pulled out, and they will discuss how to maintain the economic benefits of the deal in the face of US sanctions.

Other issues are trickier.

French officials say Mr Macron will push Russia to enlarge the so-called "Astana process" on Syria beyond the Russia-Iran-Turkey trio that's managed it so far. And he'll ask for greater efforts to implement the Minsk accords in Ukraine.

He's not not likely to get far, says Mr Fyodor Lukyanov, head of Russia's Council on Foreign and Defence Policy, which advises the Kremlin.

"There's nothing to expect from this visit," he said. "Maybe there is some small chance of some progress on Syria, but on Ukraine, we're in a total dead end."

Ms Kastoueva-Jean of the IFRI said even if there's little advance on political issues, the leaders can fall back on stressing economic issues.

France has been the largest investor in Russia since 2014, and has the second-largest stock of foreign investment in Russia after Germany.

French exports to Russia rose 8 per cent in 2016 to 4.9 billion euros (S$7.74 billion), after falling 33 per cent in 2015 as a result of EU sanctions imposed on Russia over its meddling in Ukraine.

Most major French companies attend the St Petersburg meeting on their own, so Mr Macron's delegation will be made up of start-ups.

The French leader will speak on Friday on a panel with the forum's other guest of honour, Japanese Prime Minister Shinzo Abe.

They are the most high-profile attendees since Dr Merkel in 2013.

"There's one big advantage to this trip because it's an economic forum and the economic relationship is holding up pretty well," Ms Kastoueva-Jean said.