European Council president Donald Tusk has warned Boris Johnson that he will not “co-operate on no-deal” ahead of a meeting between the two at the G7 summit.
Tusk also said he hoped the prime minister would not go down in history as “Mr no-deal”.
Johnson is expected to set out his plans for Brexit in talks with Tusk, building on visits in recent days to the leaders of Germany and France.
Speaking at the summit in France before Johnson’s arrival, the former Polish prime minister 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.”
Before setting off for the coastal resort of Biarritz, Johnson warned Brexit critics they are “gravely mistaken” about the UK losing its place on the world stage as he prepared for his first international summit and trade talks with US president Donald Trump.
The prime minister will meet Trump in the margins for their first face-to-face discussion since he entered Downing Street.
Ahead of the summit, which begins on Saturday and continues until Monday, 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.”
His comments will be seen as a rebuke to Emmanuel Macron after the French president suggested that a post-Brexit trade deal with the US could see Britain as a “junior partner” in a position of “historic vassalisation”.
Johnson will meet the US president – who has repeatedly praised his leadership qualities – on Sunday morning.
The pair spoke on the phone on Friday evening ahead of their meeting, their fourth official phone call since Johnson took office a month ago and the second call this week.
In his first face-to-face meeting with Tusk, the prime minister will spell out his absolute commitment to getting the UK out of the European Union on October 31.
It follows talks with German chancellor Angela Merkel on Wednesday and Macron on Thursday after which the prime minister said the “mood music” was positive, but getting the changes he wants to the Withdrawal Agreement would not be easy and he was “telling people not to hold their breath” for a breakthrough.