DONALD Trump has warned Boris Johnson that he might not be able to close a Brexit deal with the EU27 because they are such tough negotiators.

The remarks by the US President at the end of a three-day G7 summit in Biarritz came as the Prime Minister admitted to being “marginally more optimistic” about the chances of securing a new withdrawal agreement.

He also expressed confidence that MPs would honour the mandate given by the public in the 2016 referendum, stressing: “It’s the job of everybody in Parliament to get this done.”

While Mr Johnson claimed his view that the Irish backstop had to go “has landed” with the powerbrokers in Brussels, he declined to elaborate on the alternative arrangements that he believes can replace Ireland’s desired insurance policy to keep the border open in the event a deal is not reached.

And the PM dodged a question about being prepared to rule out suspending Parliament to force Brexit through, saying only: “I hope friends and colleagues in Parliament will be supportive of our efforts to get this thing done, to get rid of the old Withdrawal agreement and get a much better deal.”

He insisted that the public and Britain’s EU partners wanted to move on from Brexit. "They want it over,” declared Mr Johnson, adding: "They are very enthusiastic about getting on with the future. They regard Brexit now as an encumbrance, an old argument. They want to talk about the new partnership that we're going to build."

At his end of summit press conference, Mr Trump waxed lyrical about his British friend and colleague but warned him that a no-deal outcome could be on the cards given how tough the EU was to negotiate with.

"They may have to get out, they may not make a deal," declared the President. "The European Union is very tough to make deals with; just ask Theresa May."

Mr Trump, who held a first formal meeting with Mr Johnson over the weekend in the French Atlantic resort, revealed how he had poked fun at the PM over the time it had taken him to finally get into No 10.

"I really believe Boris Johnson will be a great prime minister. We really like each other. And we had a great two and a half days. I have been waiting for him to be Prime Minister for about six years. I told him: ‘What took you so long?'"

He added: "His time is right; it's the right time for Boris."

In response, Mr Johnson said while the EU were tough negotiators "that doesn't mean we won't do a deal".

He added: "It will be difficult, there is a substantial disagreement, but my job is to make our case."

In recent days, the PM held talks with Germany's Angela Merkel, France's Emmanuel Macron and European Council chief Donald Tusk, which had left him more upbeat about the prospect of reaching an agreement.

Yet major stumbling blocks remain not only in Brussels but also at Westminster with opponents of a no-deal Brexit mobilising to prevent Mr Johnson meeting his pledge of leaving on October 31 “do or die”.

Earlier, UK officials urged EU leaders not to listen to the “very wrong messages” put about by MPs seeking to block a no-deal Brexit, making clear Britain’s withdrawal from the EU could not be stopped.

One insider stressed: “Politicians don’t get to choose which public votes they respect.”

He explained: “The Prime Minister has been very clear to European leaders that he’s seen in the last week that the idea that Brexit can be stopped is incorrect, and we are leaving on October 31.

“He thinks EU leaders should not be listening to the very wrong messages emerging from some parliamentarians, who think that they will stop Brexit.”

Meanwhile, Nicola Sturgeon accused Mr Johnson of "behaving in a kind of carefree, shrug of the shoulders, reckless manner".

The First Minister said: "He's gone in the matter of a few weeks from saying that a no-deal Brexit in his view was a million to one chance, to now saying it's touch and go which suggest to me he's making it up as he goes along.

"That's not acceptable because the consequences of this are so serious for our economy, for our society, for the livelihoods and living standards of people the length and breadth of the UK that that's just not good enough," she added.

Next week, Holyrood is set to step up its opposition to a no-deal Brexit when MSPs return from their summer recess.

Scottish Greens and Liberal Democrat MSPs have already signalled they will support the SNP Government's motion, stating "the Scottish Parliament agrees that the UK should in no circumstances leave the EU on a no-deal basis", ensuring it will pass.

In other developments:

*Helen McEntee, Ireland's European Affairs Minister, denied the current Brexit deal was dead, insisting the only way of avoiding a no-deal Brexit was for the UK to back the Withdrawal Agreement;

*senior EU figures warned the PM that failing to pay the £39 billion divorce bill would damage UK-EU relations and jeopardise future trade talks and

*Mr Johnson declined to express confidence in Commons Speaker John Bercow ahead of the likely parliamentary showdown over Brexit, insisting it was not the PM’s role to do so.