LONDON (AFP) - United States President Donald Trump once again waded into Britain's Brexit debate on Sunday (June 2), the eve of a state visit to London, urging Prime Minister Theresa May's successor to leave the European Union with no deal.

Whoever takes over as Britain's next prime minister should not be afraid to "walk away" from negotiations with Brussels and should refuse to pay the agreed divorce bill, he told the Sunday Times newspaper.

The intervention comes after Mr Trump used another newspaper interview to declare that former foreign minister Boris Johnson would be an "excellent" replacement for Mrs May.

Britain is rolling out the red carpet for the President this week, starting with a private lunch with Queen Elizabeth II and a state banquet at Buckingham Palace on Monday.

But large protests are also planned over what London Mayor Sadiq Khan described as Mr Trump's "divisive behaviour", while opposition politicians are boycotting the banquet.

'I WOULDN'T PAY'

Mr Trump embarrassed Mrs May with outspoken remarks on Brexit during his visit to Britain last year. On Sunday, he again urged the next government to follow his own negotiating rule book.

"If they don't get what they want, I would walk away... If you don't get the deal you want, if you don't get a fair deal, then you walk away," he said.

Mrs May has already agreed to pay £39 billion (S$67.7 billion) to cover Britain's liabilities as it moves to sever four decades of EU membership.

But Mr Trump said: "If I were them I wouldn't pay US$50 billion (S$68 billion). That is me. I would not pay, that is a tremendous number."

Mrs May agreed on a divorce agreement with Brussels last November, but British MPs have rejected it three times and she has had to delay Brexit twice.

She has now been forced out and her Conservative party is beginning the process of finding a new leader, with 13 candidates already declared.

Mr Johnson, one of the front runners, is among several to say Britain should leave the EU on Oct 31 with or without a deal.

They are under pressure from the Brexit party, the latest political vehicle of anti-EU populist leader Nigel Farage, which came top in European Parliament elections last month.

Mr Trump said he believed Mr Farage should play a role in negotiating Brexit with the EU, saying he had a "lot to offer".

CONSERVATIVES DIVIDED

Three years after Britons voted by 52 per cent to 48 per cent to leave the EU in 2016, the government and lawmakers are still wrangling over the issue.

Brexit day was originally set for March 29. But Mrs May delayed it twice to avoid a damaging "no-deal" exit, under which Britain would separate from its closest trading partner with no new arrangements in place.

Her own Conservative MPs had blocked the deal because they feared it would leave Britain too closely tied to the EU.

Many candidates to replace her want to renegotiate the text on EU withdrawal, although the EU has explicitly ruled that out. If they cannot, several say Britain must leave anyway.

However, one front runner, Environment Secretary Michael Gove, was reported on Sunday to be ready to delay Brexit again to avoid a "no-deal" scenario.

Meanwhile, voters across the country are divided.

Although Mr Farage won the most votes in European elections, the Liberal Democrats, who want a new referendum to reverse Brexit, came second.

TRADE TALKS

Britain's future trading relationship with the US will be crucial to its post-Brexit success and is likely to be discussed during Mr Trump's talks with Mrs May at Downing Street this week.

But some here fear Britain would be steamrolled by the far bigger US into accepting an unbalanced accord, especially given Mr Trump's "America First" stance in shaking up trade ties with Mexico, Canada, Japan and China.

US Ambassador to Britain Woody Johnson told BBC television that Washington was already preparing the way for a trade deal and it would be done "as expeditiously as any agreement we've ever had".

He said he would expect Britain to be open to US agricultural products. When asked about access of US firms to Britain's cherished state-run health service, he said: "All things that are traded would be on the table."