Kirk was a “giant of his generation,” and a “champion of liberty,” Trump said at the beginning of his remarks during a 9/11 ceremony at the Pentagon, which was one of the targets of the Al-Qaeda attacks that sparked two decades of deadly conflict.
The US president announced that he would soon posthumously award Kirk the Presidential Medal of Freedom – the country’s highest civilian honour.
Speaking at the same ceremony, defence secretary Pete Hegseth said that “like those on 9/11, you will never be forgotten.”
Kirk – a close ally of Trump – was shot in the neck while speaking at an event at Utah Valley University on Wednesday.
Vice president JD Vance cancelled a trip to New York for 9/11 commemorations so he could meet with Kirk’s grieving family in Utah.
Later on Thursday, Trump travelled to his hometown of New York to attend a baseball game at Yankee Stadium, where he received both cheers and boos from the crowd.
Memorial events for 9/11 were held at Ground Zero in Manhattan where the World Trade Center’s twin towers were destroyed in coordinated attacks that also saw a jetliner crashed into the Pentagon.
Another jet crashed into the Pennsylvania countryside when passengers overran the hijacker and took control of the aircraft.
‘Same hate’
Several mayoral candidates took part in commemorations in New York that marked a brief respite from a bitter battle to be the city’s next leader.
Two days ago, former governor and independent candidate Andrew Cuomo criticised his Democratic rival Zohran Mamdani for giving an interview to a left-wing streamer who had said in 2019 that the US deserved 9/11. Cuomo said it showed that Mamdani does not deserve to be mayor.
Mamdani’s campaign hit back that “to suggest that Zohran Mamdani – who is poised to become New York’s first Muslim mayor – somehow supported 9/11” is “vile” and “dangerous.”
Mamdani holds a 22-point lead in the race, according to the latest polling from The New York Times and Siena.
Incumbent mayor Eric Adams tied the killing of Kirk with 9/11 on Thursday, saying: “It’s the same hate that drove two planes into the World Trade Center that drove a bullet through the neck of Charlie Kirk.”
“That assassination cut at the heart of what we are as Americans,” Adams said.
“If we don’t pause for a moment on 9/11 to state that we’re better than that as Americans, we’re better than that as human beings, then we’re going to find ourselves in a dark place.”
New York marked a citywide moment of silence at 8.46am (1246 GMT), when hijacked Flight 11 struck the North Tower of the World Trade Center 24 years ago.
Places of worship across the city then sounded their bells to mark the impact as families of the victims read the names of those killed at ground zero.
The official death toll was 2,977 including the passengers and crew of the four hijacked planes, victims in the twin towers, firefighters and personnel at the Pentagon. The death toll excludes the 19 Al-Qaeda hijackers.