Donald Tusk launched a scathing attack on Donald Trump and Boris Johnson as world leaders arrived in France for the G7 summit.
The European Council president warned Mr Johnson could go down in history as "Mr No Deal" before the prime minister had even touched down.
But speaking on the plane to Biarritz, Mr Johnson retaliated by suggesting a failure to reach a Brexit agreement would also reflect badly on Mr Tusk.
The prime minister is preparing for his first international summit and meeting with US president Donald Trump since he entered Downing Street.
Ahead of the summit, which continues until Monday, Mr Johnson warned his Brexit critics they were “gravely mistaken” about the UK losing its place on the world stage.
Welcome to live updates from The Independent on the three-day G7 summit in Biarritz, France.
Boris Johnson was preparing for his first international summit and trade talks with Donald Trump.
The meeting of leaders from major economies in Biarittz will see Mr Johnson set out his plans for Brexit in talks with Donald Tusk, the president of the European council.
Ahead of the summit, Mr Johnson said: "Some people question the democratic decision this country has made, fearing that we will retreat from the world. Some think Britain's best days are behind us.
"To those people I say: you are gravely mistaken."
Mr Johnson and Mr Trump spoke by phone on Friday evening ahead of the meeting. It was their fourth official phone call since Mr Johnson entered Downing Street a month ago and the second call this week.
A Downing Street spokesman said: "They discussed topics on the agenda for the summit, including foreign policy issues and global trade."
Jeremy Corbyn, the Labour leader, has warned Mr Johnson not to push Britain into a "Trump first" Brexit as the prime minister heads for his first face-to-face meeting with the US president. Andrew Woodcock, our political editor, has the story:
Boris Johnson warned not to push Britain into 'Trump first' Brexit
The prime minister meets the US president at the G7 meeting of world leaders in Biarritz this weekendLeaders of the G7 nations will meet amid a brewing confrontation between the US and China over protectionism.
Emmanuel macron, the French president, will have a tough task of delivering meaningful progress on trade, Iran and climate change.
Mr Macron wants the leaders of Britain, Canada, Germany, Italy, Japan and the United States to focus on the defence of democracy, gender equality, education and climate change, and has invited leaders from Asia, Africa and Latin America to join them for a global push on these issues.
But with the trade war between China and the US escalating, European governments struggling to defuse tensions between Washington and Tehran and global condemnation growing over illegal fires in the Amazon, his agenda could be eclipsed.
Mr Trump's history of belligerence towards multilateral gatherings, which brought last year's G7 summit to an acrimonious conclusion, means there is little hope for substantive agreements.
France has already decided that, to avoid another failure, there will be no final communique.
Mr Trump's walkout at the Charlevoix summit in Canada last year prompted foreign policy observers to dub the Group of Seven nations the G6+1.
Boris Johnson will urge world leaders to take tougher action on climate change and environmental protection, Andrew Woodcock, our political editor writes, as the prime minister announces a cash boost for research into flying taxis and delivery drones.
Boris Johnson gives cash boost for research into flying taxis and delivery drones
Innovators offered the chance to bid for £300m of government and industry cashOn Friday, EU leaders piled pressure on Jair Bolsonaro, the president of Brazil, over fires raging in the Amazon rainforest.
Mr Macron, the French president, said Mr Bolsonaro had lied in playing down concerns about climate change at a G20 summit in Japan in June, and threatened to veto a trade pact between the European Union and the Mercosur bloc of South American countries.
Greenpeace called the deforestation an emergency that highlighted the G7 leaders' need to act on ending fossil fuels and protecting forests.
"Once again, Emmanuel Macron is making bold statements which have yet to be matched by actions," said Greenpeace France Executive Director Jean-François Julliard.
"France and other developed countries are responsible for the dire Amazon situation through their economies and contribution to imported deforestation, fuelled by ill-designed policies in sectors like agriculture, timber and bio-energies."
Hours before leaving for Biarritz, Mr Trump reacted angrily to China's move to impose retaliatory tariffs on more US goods, even saying he was ordering US companies to look at ways to close their operations in China.
The president cannot legally compel US firms to abandon China immediately.
"Our Country has lost, stupidly, Trillions of Dollars with China over many years," Mr Trump tweeted. "We don't need China and, frankly, would be better off without them."
Xi Jinping, China's president, is not among the Asian leaders invited to the Biarritz summit.
Here's more on how US allies have nearly given up on the idea the G7 summit will produce unity and consensus:
World leaders believe ‘it’s pointless’ attempting to show unity with Trump at G7
‘Macron is hoping to get out of Biarritz with no blood on the floor’Japanese prime minister Abe Shinzo has arrived for the G7 summit amid escalating tensions with South Korea.
South Korea canceled a deal to share military intelligence, mainly on North Korea, after a trade dispute between the two countries.
Relations between two countries, both allies of the US, are at their lowest point since they established diplomatic ties in 1965.
Donald Trump has landed in France for the G7 summit.
Hundreds of protesters are marching as the G7 leaders arrive in the French resort town of Biarritz.
Protesters planned to cross into Spain from the French border village town of Hendaye.
As the march began, they held cardboard signs aloft with pictures of Earth, protesting against climate policies they blame on the world's G7 countries.
Mr Macron, the French president and host, put the Amazon fires at the top of the agenda for the weekend meeting.
Donald Tusk, the president of the European Council, has said under no condition can he agree with Donald Trump's proposal to bring Russia back into the G7.
In a further thinly veiled dig at Mr Trump, Mr Tusk also said G7 leaders should make more of an effort to find common language on Iran and said trade wars among G7 members would lead to already weakened trust.
He said if Mr Trump was using tariffs as a political tool it could be risky for the whole world.
Mr Tusk said "the last thing we need and want is confrontation with our best ally, the United States."
But he said France can count on EU loyalty for one of its most valuable exports.
Mr Tusk said this year's summit will be an "unusually difficult" meeting and warned it could be the last moment to restore unity among the G7 countries.
Speaking ahead of his meeting with Mr Johnson, Mr Tusk said: "He will be the third British Conservative prime minister with whom I will discuss Brexit.
"The EU was always open to co-operation when David Cameron wanted to avoid Brexit, when Theresa May wanted to avoid a no-deal Brexit and we will also be ready now to hold serious talks with Prime Minister Johnson.
"One thing I will not co-operate on is no deal. I still hope that Prime Minster Johnson will not like to go down in history as 'Mr No Deal'.
"We are willing to listen to ideas that are operational, realistic and acceptable to all member states including Ireland, if and when the UK government is ready to put them on the table."
France is pressing the White House to endorse a global pledge at the G7 summit to better fight against the spread of hate speech on the internet.
Cedric O, a French official in charge of digital economy, told reporters that the other six nations in the G7 have already backed the pledge, as have Google and Facebook.
The US did not endorse a similar pledge after the mosque attack in Christchurch, New Zealand, earlier this year.
Mr O said the pledge includes a commitment to fight terrorist and hate speech on the internet, transparency on the process, and defense of freedom of expression.
Donald Tusk says "under no condition" can the G7 welcome Russia back as Mr Trump suggested
Angela Merkel, the German chancellor, has said the G7 leaders "cannot be silent" in the face of fires sweeping parts of Brazil's Amazon and will call for everything to be done to stop fires in the rainforest.
Germany is backing the French president Emmanuel Macron's call to discuss the fires at the weekend's French-hosted G7 summit.
Ms Merkel said in her weekly video message released Saturday: "Emmanuel Macron is right — our house is burning, and we cannot be silent."
She said leaders are "shaken" by the fires and that they will discuss "how we can support and help there, and send a clear call that everything must be done so that the rainforest stops burning."
Amid a series of policy and trade disagreements, which she didn't address explicitly, Ms Merkel said that "talking to each other is always better than about each other — and the G7 is an excellent opportunity for that."
Biggest names in fashion to meet at G7 summit to improve sustainability
‘We have to work collectively’Germany says impeding a trade deal between the European Union and South American trade bloc Mercosur won't help reduce the destruction of rainforest in Brazil.
On Friday, Mr Macron, the French president, threatened to block the recently agreed trade deal with Mercosur, which also includes Argentina, Paraguay and Uruguay. Ireland joined in the threat.
Ms Merkel, the German chancellor, has made clear she shares Mr Macron's concern about the fires.
But her government said its trade section "includes an ambitious sustainability chapter with binding rules on climate protection," in which both sides committed to implementing the Paris climate accord.
It added: "The non-conclusion [of the deal] is therefore from our point of view not the appropriate response to what is currently happening in Brazil."
