By CHARLIE SPIERING, SENIOR POLITICAL REPORTER IN LONDON, UNITED KINGDOM

President Donald Trump honored his murdered friend Charlie Kirk on foreign soil Thursday, revealing he once told the conservative firebrand he had presidential potential.

'A great American was heinously assassinated for speaking his mind,' Trump declared during his UK press conference with Prime Minister Keir Starmer. 'Incredible future -- gone.'

Kirk, 31, was gunned down by a lone assassin while addressing students at Utah Valley University last week. The rising conservative star's death has sent shockwaves through the political world.

Trump thanked British supporters who rallied in London mourning Kirk's assassination, calling his murdered friend 'a great young mind' whose voice was silenced by violence.

Trump added that he appreciated British citizens who expressed their condolences after his assassination.

'Charlie was a great person,' he said.

The president referred to rallies of conservatives in the United Kingdom after more than 100,000 protestors descended in London on Saturday to protest Starmer prior to Trump's state visit.

Activists rallied for free speech but protesters also featured messages mourning Kirk's death.

US President Donald Trump during a press conference with Prime Minister Sir Keir Starmer at Chequers, near Aylesbury in Buckinghamshire

Charlie Kirk, the American conservative activist and commentator. He is best known as the founder of Turning Point USA

Prime Minister Starmer also expressed his condolences to Trump, noting that the assassination sent 'shockwaves through the world.'

'I know he was a friend of the president, and I reached out straight away to the president,' he said.

The president confirmed his plans to attend Kirk's funeral on Sunday, set for the Phoenix area State Farm Stadium in Glendale, Arizona that holds over 63,000 people.

'He just wanted to take care of youth. He loved youth,' he said. 'I've never seen anybody relate to youth like Charlie. And they liked Charlie. And they related to him. And they're devastated.'

The president revealed that he often told Kirk that he could be president one day.

'I told him, I said, 'you have a good shot someday at being president,'' he said.

The president spoke about the importance of defending Western values that included freedom of speech.

Protesters carry a poster depicting the late US political activist Charlie Kirk during the "Unite The Kingdom" rally

A west London pub temporarily rebranded to "The Trump Arms" to mark Donald Trump's state visit this week.

'I hope that together, our nations can lead a movement to defend the lead a movement to defend the glorious traditions of freedom on both sides of the Atlantic,' he said.

The president volunteered that Kirk was the one who encouraged him to get on TikTok, after he was asked about whether the algorithm of the social media platform continue to be controlled by China.

Trump said he would speak to President Xi about the social media platform that was banned by Congress and signed by former President Joe Biden.

'I like TikTok, it helped get me elected,' Trump said. 'In fact, Charlie said, 'Sir, you ought to get on TikTok. You'd be great.''

Trump said the platform had 'tremendous value' and that there would be 'a lot of unhappy youth' if the platform was banned.

Donald Trump grateful to British citizens for tribute to Charlie Kirk