Trump advocates no-deal Brexit on eve of UK visit

"[Johnson] would do a very good job - he would be excellent. He has been very positive about me and our country," Trump said in his endorsement of one of the 13 candidates vying to be the next British prime minister after Theresa May steps down on 7 June.

"I like Nigel [Farage] a lot. He has a lot to offer - he is a very smart person," Trump added.

"They [the British government] won't bring him in [to Brexit negotiations] but think how well they would do if they did. They just haven't figured that out yet," the US president said.

"He is a terrific person. Really, a terrific person," Trump added.

Johnson, a former foreign minister, is a hard-Brexiteer who advocates leaving the EU with no withdrawal agreement on 31 October.

Farage, who also advocates a no-deal exit, has said he wants to be part of Britain's EU negotiation team due to his Brexit Party's victory in last month's European Parliament elections.

Trump added that Britain should refuse to pay the €45bn [$50bn] that it previously agreed to in order settle its EU budgetary commitments.

"I wouldn't pay $50bn. That is me. I would not pay," he said.

"If you don't get the deal you want, if you don't get a fair deal, then you walk away," he added.

Trade talks

Johnson and Farage have both made promises of a free-trade deal with America to replace lost trade with Europe in future.

"One of the advantages of Brexit is the fact that now you can deal with the No. 1 country by far," Trump said in his interview.

"There's an opportunity for a very big trade deal at some point in the near future," he also told press in the US on Sunday.

His British ambassador, Woody Johnson, told the BBC the same day that the British agriculture and healthcare sectors should be opened up to US firms as part of a trade accord.

Asked if that meant US products such as chemically-cleaned chicken should be allowed for sale in Britain, ambassador Johnson said: "There will have to be some deal where you give the British people a choice ... if the British people like it, they can buy it; if they don't like it, they don't have to buy it."

Chlorinated chicken has been banned by the EU since 1997 on health grounds, but ambassador Johnson said "American food supply is as safe as anything in Europe".

Asked if the British National Health Service (NHS) should be broken apart to let in US competitors, Johnson also said: "All things that are traded would be on the table ... I would think so".

Second state visit

The comments came ahead of Trump's second visit to the UK.

He is to meet the British queen at a banquet on Monday, ride around London in high pomp on Tuesday, then attend a World War Two memorial event on Wednesday.

Some 250,000 people are expected to protest against the US president on his London tour, even though British police have created an 'exclusion zone' that will keep most of them out of sight.

May's office said his visit would "strengthen our already close partnership" and the "the strong and enduring ties between our countries".

"We are the largest investors in each other's economies and our strong trading relationship and close business links create jobs, opportunities and wealth for our citizens," it added.

But for his part, British health minister Matt Hancock, who also wants to be prime minister, drew a red line around the NHS.

"I love our NHS - it's been there for me and my family when we have needed it most, and I want to make sure it is always there for all families ... the NHS is not for sale," he said.

The head of the opposition Labour Party, Jeremy Corbyn, and the deputy leader of the opposition Liberal Democrats, Jo Swinson, were more outspoken.

"Trump's attempt to decide who will be Britain's next prime minister is an entirely unacceptable interference in our country's democracy," Corbyn, who is boycotting Monday's royal banquet, said.

"It shouldn't come as a surprise that Donald Trump backs Boris - they're cut from the same cloth," Swinson said.

"They're both unqualified to lead, both revel in offending people and both represent the strain of nationalism and populism that we need a liberal movement to stand up to," Swinson added.

Labour's London mayor, Sadiq Khan, also lashed out at Trump's values.

"Trump is just one of the most egregious examples of a growing global threat. The far-right is on the rise around the world," Khan told The Observer newspaper on Sunday.

"Viktor Orban in Hungary, Matteo Salvini in Italy, Marine Le Pen in France, and Nigel Farage here in the UK are using the same divisive tropes of the fascists of the 20th century to garner support, but with new sinister methods to deliver their message," he added, referring to popular far-right EU politicians.