The leaders of France, the US, Canada, Britain, Germany, Italy and Japan are heading to France this weekend where they will face a litany of thorny issues at their meeting in the post Atlantic beach town of Biarritz.

The French government is planning to use this weekend's G7 summit to put pressure on the Brazilian government to stop forest fires that are devastating large parts of the Amazon rainforests.

Environmental protection is on the agenda at the summit of the seven most powerful countries, but the issue has been given added urgency by the Amazon fires.

Also high on the agenda is a Joint Comprehensive Plan of Action (JCPOA) - a nuclear deal signed by Iran, the EU, China, Russia, and the US in 2015.

The agreement has since all but collapsed after US President Donald Trump pulled the US out of the deal in May 2018 and reimposed sanctions that have wreaked havoc on the Iranian economy.

French President Emmanuel Macron met Iran's Foreign Minister Javad Zarif earlier today for last-minute talks trying to soothe tensions between Tehran and Washington.

"President Macron made some suggestions last week to President (Hassan) Rouhani and we believe they are moving in the right direction, although we are not definitely there yet," Mr Zarif said after the talks.

"We're at a critical moment," Mr Macron had warned on Wednesday, acknowledging that Iran is "laying out a strategy for exiting the JCPOA," originally designed to rein in the country's nuclear ambitions.

Biarritz, France

Mr Macron's diplomacy is a delicate task, with France seeking a rollback on some of the US measures imposed on Iran as part of Mr Trump's "maximum pressure" policy towards the Islamic republic, which says its nuclear programme is peaceful.

French diplomats have raised the idea of US waivers on sanctions affecting Iranian oil exports to India and China, or a new credit line for Tehran that could help the struggling economy.

That prompted Mr Trump to accuse Mr Macron of sending Tehran "mixed signals" in his attempt to broker fresh talks between the longtime adversaries.

But Mr Trump appears to be the outlier among America's G7 partners on Iran, despite speculation that British Prime Minister Boris Johnson, who claims a close personal rapport with the US leader, might be more amenable to endorsing his stance.

A diplomatic source said today the UK would continue to back the 2015 nuclear deal, which it helped broker, as the "best way" of preventing Iran from obtaining a nuclear weapon.

Tensions are expected between the French and the US leaders amid threats of tariffs 

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Iran is just one of a host of issues where G7 members find themselves at loggerheads, upending what used to be a cosy club of rich nations.

Mr Trump is set to arrive in the beachside resort of Biarritz tomorrow already riled by a new French law that will increase taxes on US internet giants such as Google and Facebook.

He is also threatening tariffs on the European automobile sector, while the climate change sceptic is not expected to contribute to Mr Macron's official agenda of fighting global warming - an issue particularly topical now, in the light of the record wildfires raging in the Amazon rainforest.

With the summit leaders vowing "concrete measures" in response to the fires, there is also a potential risk of a diplomatic clash with Brazil's president Jair Bolsonaro.

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Mr Bolsonaro has already criticised the move to address the fires at the G7 summit without any participation by Brazil, saying it reflected a "colonialist mentality".

Mr Macron, who is hosting the G7 summit, accused his Brazilian counterpart of lying on pledges in June to help fight global warming.

"Given the attitude of Brazil over the last weeks, the president can only conclude that President Bolsonaro lied to him at the Osaka (G20) summit," a French presidential official said.

As if tensions before the leaders meet had not been high enough, China fired the latest salvo in its trade war with the US, announcing new tariffs on $75bn of American imports just before the summit.

In a sign of the meeting's lowered ambitions, French officials have already scrapped any joint declaration at the end of the summit, breaking a longstanding G7 tradition.