Donald Trump has said that if he returns to the White House China would not dare provoke him because President Xi Jinping knows the Republican is “crazy”.

Speaking to the Wall Street Journal’s editorial board, Trump said that if elected president next month, he would impose tariffs on China if it sought to blockade Taiwan.

“I would say: if you go into Taiwan, I’m sorry to do this, I’m going to tax you at 150% to 200%,” he said.

On the campaign trail, the Republican candidate has argued that America’s adversaries would not act against US interests under a new Trump presidency because they would fear a forceful, even unpredictable, response.

He told the Wall Street Journal’s editorial board he would not have to use military force to prevent a blockade of Taiwan, because President Xi “respects me and he knows I’m [expletive] crazy”.

“I had a very strong relationship with him,” Trump said of President Xi. “He was actually a really good, I don’t want to say friend – I don’t want to act foolish, ‘he was my friend’ – but I got along with him great.”

“He’s a very fierce person,” Trump added.

The former president also cast his relationship with Russian President Vladimir Putin in a positive light, saying: “I got along with him great.”

But Trump – who has previously been criticised for praising the Russian leader – said he had threatened him not to invade Ukraine.

He told the Journal that he said to Putin: “’I’m going to hit you right in the middle of fricking Moscow.’ I said, ‘We’re friends. I don’t want to do it, but I have no choice.’ He goes, ‘No way.’ I said, ‘Way.’

“I said, ‘You’re going to be hit so hard, and I’m going to take those [expletive] domes right off your head.’ Because, you know, he lives under the domes.”

With his vows to wage trade wars and end US involvement in the Russia-Ukraine war, Trump has branded his foreign policy America First, though detractors say it is isolationist.

The Republican’s choice of JD Vance as his running mate alarmed Ukraine’s allies, as the Ohio senator staunchly opposes sending any more US aid to the country.

Trump, whose hardline immigration stance is central to his campaign, told the Wall Street Journal: “I want a lot of people to come in, but I want them to come in legally.”

Asked about his plan for mass deportations of illegal immigrants, he said: “I don’t want to go too much into clarification, because the nicer I become, the more people that come over illegally.”

Trump also defended the “zero tolerance” migrant family-separation policy that was used during his administration.

“I said, ‘We’re going to separate your family.’ It doesn’t sound nice, but when a family hears they’re going to be separated, you know what they do? They stay where they are, because we couldn’t handle it.

“But the interest from the heart, yeah, something’s going to be done. I mean, there’s some human questions that get in the way of being perfect, and we have to have the heart, too. OK?”

The Wall Street Journal also asked Trump about his remark on Fox News this week that the “radical left” in the US poses more of a threat than foreign actors.

“I think the bigger problem is the enemy from within,” Trump said in an interview with the network, referring to “sick people, radical left lunatics” who he said could cause trouble around the election.

Speaking to the Wall Street Journal, he cited President Joe Biden’s remark this month that he is not certain if the election will be peaceful. Biden was referring to Trump supporters like those who rioted at the Capitol in 2021.

“If you were to reach the presidency again, would you of course rule out using the military to move against your enemies?” Wall Street Journal columnist Peggy Noonan asked Trump.

“Of course I wouldn’t. But now, if you’re talking about you’re going to have riots on the street, you would certainly bring the National Guard in,” Trump said.