De Niro apologized Monday - but on America's behalf to Canadian Prime Minister Justin Trudeau, whom Trump ripped Saturday as "very dishonest and weak" after the US refused to sign the joint communique from global leaders attending the Group of Seven summit in Quebec.
De Niro was introducing Bruce Springsteen, who is starring in a Broadway production of his own, which has sold out tickets for months.
Robert De Niro introduces a performance by Bruce Springsteen at the 72nd annual Tony Awards at Radio City Music Hall in NY.
Singapore Agreement Will End Cold War, S. Korea President Says
In a news conference following the summit, Trump also praised North Korea's beaches "from a real estate perspective". Beijing's participation in the penalties is a key to keeping them in play against Kim's regime.
With the audience of theatre actors, directors and producers shrieking and rising to their feet in applause, De Niro said: "It's no longer down with Trump".
This is not the first time Mr Trump has responded to a Hollywood star attacking him during a speech. (Pictured at the 2005 Tribeca Film Festival).
De Niro, who has been an outspoken critic of Trump since the 2016 presidential election, said "f-- Trump" on stage at the Tony Awards Sunday night, and received a standing ovation. In January of this year, the actor called Trump a "f**king idiot" in a profanity-laced rant. While in Toronto Tuesday morning, De Niro told Canadians he was sorry for Trump's behavior.
"It's a disgrace. And I apologise to Justin Trudeau and the other people at the G7".