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

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

“I would say, if you go to Taiwan, I’m sorry, I’ll tax you 150% to 200%,” he said.

During the campaign, the Republican candidate argued that America's adversaries would not act against U.S. interests under a new Trump presidency because they would fear a forceful, even unpredictable response.

He told the Wall Street Journal editorial board that he didn't need to use military force to prevent a blockade of Taiwan because President Xi “respects me and knows I'm (expletive) crazy.”

“I had a very close 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 sound stupid, 'he was my friend' – but I got along great with him.”

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

The ex-president also expressed his relationship with Russian President Vladimir Putin positively: “I got along really well with him.”

But Trump – who has previously been criticized 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 beat you up in the middle of Moscow.' I said, 'We're friends.' I don't want to do it, but I have no choice.' He says, “No way.” I said, “Away.”

“I said, 'You're going to get hit so hard and I'm going to take these (swearing) domes right off your head.' Because, you know, he lives under the domes.”

With his promise to wage trade wars and end U.S. involvement in the Russia-Ukraine war, Trump has described his foreign policy as “America First,” even as critics say it is isolationist.

The Republican's choice of JD Vance as his running mate worried Ukraine's allies, as the Ohio senator strongly opposes sending more U.S. aid to the country.

Trump, whose tough immigration policies are the focus of 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 to mass deport illegal immigrants, he said: “I don't want to go into too much education because the nicer I get, the more people come over illegally.”

Trump also defended the “zero tolerance” policy on separating migrant families that was implemented during his time in office.

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

“But the interest that comes from the heart, yes, something is being done. I mean, there are some human issues that get in the way of perfection, and we have to have the heart too. OK?”

The Wall Street Journal also asked Trump about his comment on Fox News this week that the “radical left” in the U.S. posed a greater threat than foreign actors.

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

Speaking to the Wall Street Journal, he cited President Joe Biden's comment this month that he wasn't sure the election would be peaceful. Biden was referring to Trump supporters like those who rioted at the Capitol in 2021.

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

“Of course I wouldn’t do that. But if you're talking about there going to be unrest in the streets, you would certainly call in the National Guard,” Trump said.