Angela Merkel, Emmanuel Macron and other world leaders – but not, apparently, Theresa May – will try to convince Donald Trump that the US should remain part of the international fight against climate change when they meet at the G7 summit.

The Prime Minister has been accused of having a “pact of silence” with the Republican billionaire over his description of climate change as a “hoax”, his plan to withdraw the US from the landmark Paris Agreement and pledge to reinvigorate the US coal industry.

A petition by Greenpeace urging Ms May to “use your influence to save the Paris climate deal” has attracted more than 155,000 signatures.

Speaking at a meeting of about 30 nations in Berlin before meeting Mr Trump at the G7 summit on 26 and 27 May, the German Chancellor said dealing with climate change must be an international effort.

“We are responsible for each other,” Ms Merkel said. “I am trying to convince doubters. There is still work to do.”

Mr Macron, the newly elected French president, will also attempt to convince Mr Trump to keep the US within the terms of the Paris Agreement, a senior French official told Reuters.

“What’s at stake is to be firm on the Paris accord,” the diplomat said, adding that Mr Macron would put his case to Mr Trump in person.

“We don’t want the US to pull out because it would be a very bad signal and lead others to pull out.”

Ms May has sent mixed messages on climate change. One of her first acts as Prime Minister was to close the dedicated climate change department and move its responsibilities into the new Department of Business, Energy and Industrial Strategy.

The Government has persistently failed on attempts to come up with an effective plan to reduce air pollution to within minimum safety standards, and its Emissions Reduction Plan – the key policy setting out how the UK will cut its greenhouse gases – is long overdue.

However it also ratified the Paris Agreement and approved the UK’s “Fifth Carbon Budget”, which sets tough emissions reduction targets.

There has been speculation that Ms May is keen to have Mr Trump as a political ally, particularly because of the talks with the European Union over Brexit. With the US on its side, the UK might be in a stronger negotiating position than if this were not the case.

This could explain her reluctance to expend political capital on climate change, particularly if she thinks it would only aggravate Mr Trump.

Donald Trump's first 100 days: in cartoons Show all 33 1 /33 Donald Trump's first 100 days: in cartoons Donald Trump's first 100 days: in cartoons Donald Trump's first 100 days in office were marred by a string of scandals, many of which caught the eye of the Independent's cartoonists Donald Trump's first 100 days: in cartoons Trump's first 100 days have seen him aggressively ramp up tensions with his nuclear rivals in North Korea Donald Trump's first 100 days: in cartoons Mr Trump has warned of a "major, major conflict" with the pariah nation lead by Kim Jong Un Donald Trump's first 100 days: in cartoons Mr Trump dropped the "mother of all bombs" on alleged ISIS-linked militants in Afghanistan, amid an escalation of US military intervention around the globe Donald Trump's first 100 days: in cartoons Mr Trump has been accused of falling short of the standards set by his predecessors in the Oval Office, including Franklin D Roosevelt Donald Trump's first 100 days: in cartoons The tycoon's ascension to the White House came at a time when the balance of power is shifting away from Western nations like those in the G7 group Donald Trump's first 100 days: in cartoons Western politicians, including the British Conservative party, have been accused of falling in line behind Mr Trump's proposals Donald Trump's first 100 days: in cartoons Brexit is seen to have weakened Britain, reducing still further any political will to resist American leadership Donald Trump's first 100 days: in cartoons Mr Trump's leadership has been marked by sudden and unexpected shifts in global policy Donald Trump's first 100 days: in cartoons Trump's controversial missile strike on Syria, which killed several citizens, was seen by some analysts as an attempt to distract from his policy elsewhere Donald Trump's first 100 days: in cartoons The President has also spent a large majority of his weekends golfing, rather than attending to matters of state Donald Trump's first 100 days: in cartoons Though free of gaffes, a visit from Chinese president Xi Jinping spotlighted trade tensions between the two states Donald Trump's first 100 days: in cartoons One major and unexpected setback came when Mr Trump's Healthcare Bill was struck down by members of his own party Donald Trump's first 100 days: in cartoons Mr Trump has been a figure of fun in the media, with his approval at record lows Donald Trump's first 100 days: in cartoons A string of revelations about Mr Trump's financial indiscretions did not mar his surge to the White House Donald Trump's first 100 days: in cartoons Outgoing President Barack Obama was accused of wiretapping Trump Tower by his successor in America's highest office Donald Trump's first 100 days: in cartoons The alleged involvement of Russian intelligence operatives in securing Mr Trump the presidency prompted harsh criticism Donald Trump's first 100 days: in cartoons The explosive resignation of Security Adviser Michael Flynn, who lied about his links to 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But the US President seemed happy enough to receive advice from Pope Francis during his visit to the Vatican.

Francis gave Mr Trump a signed copy of a message of peace, called “Nonviolence: A Style of Politics for Peace”, and a copy of his 2015 encyclical letter on the need to protect the environment from the effects of climate change.

“Well, I’ll be reading them,” Mr Trump said.

The Sierra Club, the largest grassroots environmental group in the US with about two million members, noted the Pope had been at the forefront of calls for action on climate change for years.

Speaking ahead of the meeting with Mr Trump, John Coequyt, the group’s global climate policy director, said the Pope’s “sentiments and actions have been echoed by nearly every other world leader around the globe, yet Trump is heading into [their] meeting as the only climate-denying world leader”.

“Trump stands on one side of this issue, while the Pope, a large majority of the American public, business leaders and the global community stand on the other,” he added.

“If one thing is already clear from this meeting, Donald Trump’s denial of the climate crisis has isolated him from the rest of the world and ceded US leadership on the most pressing issue of our lives.”

The Trump administration had been due to decide whether to remain a signatory of the Paris Agreement before the G7 meeting, but two internal meetings to discuss the issue were postponed without explanation.

In November, Fiji is due to be the official host of talks about climate change involving about 200 countries, held in Bonn, Germany, for logistical reasons.

Frank Bainimarama, Fiji’s Prime Minister, suggested everyone was worried about what Mr Trump would ultimately decide to do.

“We have an elephant in the room,” he said. “That is uncertainty over the position of the United States.”

Downing Street did not immediately respond to a request for comment.