British Prime Minister Boris Johnson, who spoke confidently in the past about the United Kingdom agreeing a satisfactory divorce deal with the European Union, has now admitted securing such an outcome will be "touch and go".

Johnson, who had previously gone on record saying the odds of him failing to land such a deal were "a million to one", said in a BBC interview that it now "all depends on our EU friends and partners".

From the sidelines of the G7 summit in France on Sunday, he said: "I think it's going to be touch and go, but the important thing is to get ready to come out without a deal."

The UK is currently slated to walk away from the bloc on Oct 31 and business and banking groups have said they want it to leave with a deal in place that guarantees tariff-free trading.

There is a deal on the table, one negotiated by former prime minister Theresa May that was thrice defeated by Parliament, but Johnson has criticized it heavily and said he could do much better.

The BBC's Europe editor, Katya Adler, said talks on Sunday between European Council President Donald Tusk and Johnson had a "genuinely positive atmosphere" and the Financial Times said the two men will meet again on the margins of the UN general assembly in New York in September to continue discussions. Both are believed to want to avoid being known to history as the person responsible for the UK leaving without a deal.

Johnson insisted in the interview issues that worry Britons, such as whether they will be able to get imported medicine in the event of a no-deal Brexit, have been taken care of but said: "I do not want… to say there won't be unforeseen difficulties."

The biggest problem for Johnson in the proposed deal negotiated by May is the so-called Irish backstop, which aims to avoid the reinstatement of a hard border between the Irish Republic and Northern Ireland by committing the UK to continue trading with the EU as if it were a full member until the two sides can agree a full trade deal. Johnson and his supporters say the arrangement could effectively trap the UK in the EU in perpetuity.

"I think, in the last few days, there has been a dawning realization in Brussels and other European capitals what the shape of the problem is for the UK," he said, suggesting that the bloc is now more open to seeking other ways to solve the problem.

He also said the UK would keep a "very substantial" part of a proposed 39-billion-pound ($47.7 billion) separation payment called for in May's proposed deal if the nation ends up having to leave without a deal.

He told ITV News: "If we come out without an agreement, it is certainly true that the 39 billion pounds is no longer, strictly speaking, owed."

Several Sunday newspapers, meanwhile, suggested Downing Street may be preparing for a mid-October general election, based on the premise that Johnson's Conservative Party might be able to force the EU back around the negotiating table if it wins a large parliamentary majority.

Johnson also met United States President Donald Trump on Sunday, to talk about a potential future trade deal between the UK and the US, something, Johnson said, the US wants in place within a year.