President Trump told reporters on board Air Force One Thursday that he would step in if New York mayoral favorite Zohran Mamdani tries to arrest Israeli Prime Minister Benjamin Netanyahu.

"Yeah, I would," the president said when asked about Mamdani's repeated threats to the US ally, without elaborating on what he would do.

"It's inappropriate."

Mamdani told the New York Times last week he would order the NYPD to cuff the Israeli leader in accordance with the International Criminal Court's warrant -- despite the US not being a member of that body.

LONDON -- Trump said he would consider giving "something back" to taxpayers from the revenue he's collecting from tariff money.

"That's a nice thing to do, but you can do that, and you can also pay down debt, because we're talking about big numbers," Trump told Martha MacCullum.

The president has previously floated giving taxpayers a rebate from the billions in tariff revenue.

LONDON -- Trump has claimed Europe pressuring China over Beijing's purchases of Russian oil could help end the war in Ukraine.

"If Europe did something with respect to China, I think China would probably maybe force an end to the war," he told Fox News host Martha MacCullum.

Trump reiterated that he is expected to speak with Chinese leader Xi Jinping Friday.

LONDON -- Trump tells MacCallum that the US could provide Ukraine air security once the war ends, clarifying his previous remarks that the military would help in the "air."

"When I said help by air, I'm talking about security after the war is settled," he explained.

"So after the war is settled, we would help secure the peace."

LONDON -- Trump said King Charles III spoke to him about peace in Ukraine during their private conversations Wednesday.

"He did. He spoke about many things. We were together for a long time, really two days," Trump told Fox News' Martha MacCallum in an interview airing Thursday afternoon.

"I think he was more interested in trade," he said. "He loves the environment too."

LONDON -- President Trump said during his joint news conference with Keir Starmer that he's willing to apply more pressure on Russia -- but only if European countries comply with boycotting Moscow's oil.

"I'm willing to do other things, but not when the people that I'm fighting for are buying oil from Russia," Trump told reporters at Chequers. "That's not, that's not playing fair with the United States. And we can't have that."

LONDON -— During his airborne gaggle, President Trump piled on ousted ABC late-night host Jimmy Kimmel

"Anybody could replace him, he had no talent," the president said when asked who he would like to see step into the 11:35 p.m. weeknight time slot.

"He had no talent. He's a whack job, but he had no talent. And more importantly, he had no ratings ...

"That's something that should be talked about for licensing, too," Trump added. "When you have a network and you have evening shows, and all they do is hit Trump ... When you go back, take a look, all they do is hit Trump ... They're an arm of the Democrat Party."

LONDON— The helicopter carrying President Trump and first lady Melania Trump to Stansted Airport for their departure to Washington had to make an unscheduled landing, the White House has confirmed.

“Due to a minor hydraulic issue, and out of an abundance of caution, the pilots landed at a local airfield before reaching Stansted Airport," press secretary Karoline Leavitt said. "The president and first lady safely boarded the support helicopter."

Air Force One departed for Joint Base Andrews about 40 minutes behind schedule.

LONDON -- President Trump has been speaking briefly to reporters on board Air Force One en route back to Washington -- and had some scathing words for London Mayor Sadiq Khan.

"He’s among the worst mayors in the world, and we have some bad ones. You can look at Chicago, I think he’s equivalent to the mayor of Chicago,” Trump said of Khan, a frequent critic of his.

“I think he’s done a terrible job. The crime in London is through the roof … on immigration he’s a disaster. But I asked that he not be there. He wanted to be there.”

WASHINGTON — Erika Kirk was unanimously elected the new CEO and chairwoman of Turning Point USA, the powerhouse conservative grassroots organization that her late husband, Charlie, co-founded in 2012, the group announced Thursday.

“In prior discussions, Charlie expressed to multiple executives that this is what he wanted in the event of his death,” Turning Point USA’s board revealed in a statement.

Erika Kirk — who runs her own nonprofit, Everyday Heroes Like You — emotionally vowed to carry on her husband’s legacy following his assassination last week.

“Charlie prepared all of us for a moment like this one. He worked tirelessly to ensure Turning Point USA was built to survive even the greatest tests,” Turning Point USA’s board added. “We will not surrender or kneel before evil. We will carry on.”

“The attempt to destroy Charlie’s work will become our chance to make it more powerful and enduring than ever before.”

Kirk, 31, was assassinated while speaking to students at Utah Valley University Sept. 10.

Authorities have since arrested Tyler Robinson, 22, and charged him with Kirk’s murder, with Utah prosecutors saying they intend to pursue the death penalty.

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President Trump and first lady Melania Trump are headed back to the United States after their visit to the United Kingdom.

Trump is the first president to have two state visits to the UK.

Trump and Melania acknowledged the cameras when boarding Air Force One.

President Trump and UK Prime Minister Keir Starmer on Thursday signed a joint memorandum of understanding on artificial intelligence (AI), civil nuclear energy and quantum technologies.

AI developments will include joint research programs as well as a space partnership between the US and UK, with emphasis on chip and data center exports along with a shift toward AI-enabled 6G technologies -- and enhanced collaboration between the US Center for AI Standards and Innovation and the UK AI Security Institute.

New nuclear policies will enhance non-proliferation and security programs, increase exports to global markets and move toward "full independence from Russian nuclear fuel by the end of 2028."

Quantum technologies, aimed at speeding up computer processing capabilities, will be deployed to "transform defense, finance, and healthcare, protect the Participants’ citizens, and create high-skilled jobs."

Within six months, the details of the memo will be put into effect. Formal discussions between the countries will happen after 12 months of its Sept. 18 signing and on a yearly basis thereafter.