"You have people coming in and I told the prime minister I would stop it, and it doesn't matter if you call out the military, it doesn't matter what means you use," Trump said.

"It destroys countries from within and we're actually now removing a lot of the people that came into our country."

The news conference brought to an end Trump's unprecedented second state visit to the UK.

In two days of pomp and pageantry, the US president was hosted at Windsor Castle by King Charles and the Royal Family, and attended a state banquet on Wednesday before his political meeting with the prime minister.

In a wide-ranging Q&A with UK and US journalists, the leaders were also asked about Palestinian statehood, free speech, the war in Ukraine, energy and other topics.

The pair touted the "special relationship" between the UK and the US, and announced a new tech deal Trump said would help the allies "dominate" in the world of artificial intelligence (AI).

The tech prosperity deal signed at Chequers will see US firms invest in the UK and boost co-operation on AI, quantum and other emerging technologies.

Trump and Sir Keir skirted around several contentious matters, including accusations of free speech being under attack in Britain, and the sacking of Peter Mandelson as the UK's ambassador to the US last week.

"I don't know him actually," Trump said, when asked about whether he had sympathy with Lord Mandelson.

In what could have been an awkward moment, Trump defused the question by handing over to Sir Keir, who fired Lord Mandelson over his links to the late convicted sex offender Jeffery Epstein.

But in one flashpoint, Trump said he had "a disagreement with the prime minister" on the subject of Palestinian statehood.

The prime minister plans to recognise Palestinian statehood ahead of next week's United Nations general assembly in New York.

Trump is opposed to such a move and accused Palestinian armed group Hamas of "putting the hostages up as bait" in Gaza.

The war in Ukraine came up in a few questions too, with Trump expressing his disappointment in Russian President Vladimir Putin over his lack of engagement with peace efforts.

"He's really let me down," Trump said.

Trump also urged Western allies to stop buying Russian oil to force Putin to the negotiating table, but did not commit to sanctioning Moscow.

There were no divisions between Trump and Starmer on action to tackle illegal migration, as the leaders projected a sense of unity and affection for each other.

Trump suggests Starmer could use military to control UK borders