US President Donald Trump will lead tributes at a memorial for slain right-wing influencer Charlie Kirk on Sunday at a 63,000-seat American football stadium, celebrating the life of a figure credited with aiding the president's re-election.

• Kirk, founder of Turning Point USA, was shot in the neck on September 10 while speaking at a Utah university.
• The suspected 22-year-old gunman cited the "hatred" he believed was stoked by Kirk, a vocal critic of transgender people and Muslims.
• The White House declared it would crack down on "domestic terrorism" by the political left, with Trump threatening to designate "Antifa" as a "major terrorist organization."