President Donald Trump's recently ousted national security adviser John Bolton criticized the administration at a private luncheon in New York City on Wednesday, criticizing the president's willingness to meet with the Taliban at Camp David and his handling of Iran and North Korea, a person who attended the event told NBC News.

The person said that Bolton never mentioned Trump by name at the luncheon, hosted by a conservative think tank, but it was "clear Bolton was making references to the president and his policies." That included the administration's plans to meet with the Taliban at Camp David in the days before the anniversary of the Sept. 11 attacks.

At the luncheon, Bolton said the planned meeting, which Trump wound up canceling on Twitter, sent a "terrible signal" and was "disrespectful" to the victims of the attacks, the person recounted.

The axed adviser also argued that the administration's failure to respond militarily to Iran striking an unmanned U.S. drone earlier this year set the stage for Iran's alleged role in the attack on a Saudi Arabian oil site over the weekend.

He also belittled the president's willingness to meet with the leaders of North Korea and Iran, saying any negotiations with those countries are "doomed to failure," the person said.

Bolton's remarks at the Gatestone Institute event were first reported by Politico. The event was scheduled before Bolton's ugly public split with the president, the website said.

The person who attended the luncheon told NBC News that Bolton seemed resolute and appeared buoyed by the reaction that he got from attendees. Other guests declined to comment on the event to NBC, saying they'd been told the event was off the record.

Reporters asked Trump about Bolton's comments later on Wednesday as he was touring the southern border at Otay Mesa, Calif.

Trump brushed off the criticism, saying, "guys like Bolton and others wanted to go into Iraq and that didn’t work out too well."

"John was not able to work with anybody," he added.

Bolton and his representative did not immediately respond to requests for comment.