Donald Trump has given his backing for Brexit, stating that the UK would be "better off without" the European Union.
The US presidential hopeful said the migration crisis had been a "horrible thing for Europe" and blamed the EU for driving it.
The Republican party's presumptive nominee for the White House said he was not making a "recommendation" but his "feeling" was that the UK should vote to sever ties with Brussels on June 23.
His intervention comes after President Barack Obama and Democratic front-runner Hillary Clinton expressed support for the UK remaining in the EU.
Trump told Fox News: "I think the migration has been a horrible thing for Europe, a lot of that was pushed by the EU.
"I would say they are better off without it, personally, but I'm not making that as a recommendation, just my feeling.
"I know Great Britain very well, I know the country very well, I have a lot of investments there.
"I would say that they are better off without it, but I want them to make their own decision."
The billionaire business tycoon's comments come after Prime Minister David Cameron said he deserved "respect" for emerging as the Republican presumptive nominee for the US presidency.
Mr Cameron has faced calls from the Trump camp to apologise after he branded the Republican's call for foreign Muslims to be temporarily banned from entering the US as "stupid, divisive, and wrong" in the Commons last December.
At a Downing Street press conference Cameron stood by his comments, but said: "It is a matter for voters in the United States to decide who they choose as their next president.
"I have to say that knowing the gruelling nature of the primaries, and what you have to go through, anyone who makes it through that extraordinary contest to lead their party into a general election certainly deserves our respect.
"What I said about Muslims, I won't change that view, I don't change that view. I am very clear that the policy idea that was put forward was wrong, is wrong, and will remain wrong, so I am very clear about that."