US President Donald Trump has used his latest interview to brand the EU as "very protectionist" and warn against a second Scottish independence referendum.

The billionaire property mogul, 71, also told the Wall Street Journal that he wanted to be "very involved" with the UK, just days after International Trade Secretary Liam Fox travelled to America to talk-up a post-Brexit free trade agreement between the nations.

"Is Scotland going to go for the vote, by the way? You don't see it. It would be terrible. They just went through hell," Trump said, referencing the last plebiscite in 2014 and talking after SNP leader Nicola Sturgeon said she will not table a Scottish independence bill in Holyrood until 2018.

The Republican, who owns luxury golf courses in Ayrshire and Aberdeenshire, added: "What would they do with the British Open if they ever got out? They'd no longer have the British Open."

Trump also stressed that he had a "very good relationship" with Prime Minister Theresa May, who was the first world leader to visit the White House after Trump's inauguration in January. "And we are absolutely looking to do a major trade deal," he said.

"I have a very good relationship with the EU people and all, but they are very, very protectionist. You know, our farmers and others can't even deal with – you know, you can't sell in. It's very unfair."

"Now, the EU was conceived to the point that they wanted to do something to compete with the United States. Well, you know, you could say that's a friendly act or an unfriendly act. But it's very protectionist."

The US president later said that he would "have to talk" to the EU "because it's not a reciprocal deal. The word reciprocal, to me, is very important," he explained.

The Transatlantic Trade and Investment Partnership (TTIP), a planned free trade agreement between the bloc and the US, is still undergoing negotiations. Trump, meanwhile, and despite his "very good" relationship with May, has delayed a state visit to the UK. He is now expected to travel to Britain sometime in 2018.