LONDON — At his first international summit as prime minister of Britain, Boris Johnson needed somehow to capitalize on his friendship with President Trump, yet show that he is not the president’s poodle and avoid falling out with Europe’s most important leaders at the same time.
On Sunday at the gathering of G7 leaders in Biarritz, France, he just about walked that diplomatic tightrope, even if he got little in the way of reassuring signals — and offered even fewer — about how Britain will confront its big, imminent challenge: Brexit.
The summit marked the arrival on the global stage for Mr. Johnson, who has promised to withdraw Britain from the European Union by the Oct. 31 deadline, with or without an agreement.
In a meeting with Mr. Trump — their first face-to-face meeting since Mr. Johnson became prime minister last month — the president praised Mr. Johnson as the “right man” to deliver Brexit, a project both leaders favor, and promised a “very big trade deal” with the United States once Britain had left the bloc.
Mr. Johnson needs a favorable trade deal with the United States to cushion economic losses from loosening ties to the bloc, Britain’s biggest trade partner.
But mindful of the sensitivities of his voters back home, Mr. Johnson responded cautiously about such a trade pact, saying that reaching an agreement “may take some time” and would require compromises from the United States, too.
Mr. Johnson also gave conflicting assessments to broadcasters of the prospects of Britain avoiding a disorderly and economically damaging exit from the European Union in the fall.
With speculation growing that Britain is heading for a general election in the fall, the new prime minister knows he must tread carefully.
Mr. Johnson has said he wants to renegotiate a Brexit deal with Brussels, but he has also moved to prepare Britain for a cliff-edge departure at the end of October. His statements in Biarritz left little clarity about the status of his efforts to renegotiate the withdrawal agreement with the European Union.
In an interview on Sunday with the British Broadcasting Corporation, Mr. Johnson said that the chances of a Brexit deal were “touch and go” and claimed that reaching an agreement “all depends on our E.U. friends and partners.”
That was seen as part of positioning on both sides of the Channel for the blame game should Britain leave the bloc without a deal. Donald Tusk, the president of the European Council, said on Saturday that Mr. Johnson “will not like to go down in history as ‘Mr. No Deal.’”
Mr. Johnson told Sky News, another British broadcaster, on Sunday that the chances of a Brexit deal were “improving.” He also said, however, that if an agreement were not struck, Britain would not be obliged to pay all the 39 billion-pound divorce bill it had promised the European Union.
The statements reflect the complicated diplomatic path that Mr. Johnson is walking as he tries to woo Mr. Trump and play hard ball with Brussels — without completely alienating European leaders. And for Mr. Johnson the summit is probably less about negotiation and more about managing expectations at home before a possible election campaign.
The prospect of a no-deal Brexit has also raised fears of chaos at jammed ports and shortages of medicines and fuel.
To avert that possibility, Mr. Johnson might be more flexible than he seemed over his demand to scrap the so-called Irish backstop in the withdrawal agreement, which would ensure that goods flowed without checks across the border between Ireland and Northern Ireland.
The London Sunday Times reported that Britain could remove the need for the backstop by taking a “sectorial approach,” aligning the economy closely on European Union rules that most affect Irish border trade, while being free to diverge in other areas.
But Mr. Johnson has stepped up preparations for a no-deal Brexit and needs Mr. Trump’s help if he is to strike a trade deal that will lessen the economic blow of a break with the European Union. Yet, the American president is not popular in Britain, and there is suspicion about the concessions he would demand for a trade agreement.
Britain’s opposition leader, Jeremy Corbyn, is already trying to paint Mr. Johnson as the American president’s poodle.
On Sunday, it became clear that there were differences between Mr. Trump and Mr. Johnson about the shape of any trade deal between Britain and the United States, including whether it would be a comprehensive pact.
Mr. Johnson pledged a “fantastic deal once we clear up some of the obstacles in our path.” Mr. Trump interrupted, promising “lots of fantastic mini-deals.”
But British critics fear that a trade deal with the United States could harm the National Health Service, by forcing an increase in its pharmaceutical prices, or allow the import of food farmed to lower standards than in Europe.
Mr. Johnson said that he had explained these objections to the president.
“Not only have I made clear of that; the president has made that very, very clear. There is complete unanimity on that point,” he said, while suggesting that there would be “tough talks ahead.”