Former White House national security adviser John Bolton slammed President Trump in front of a private audience, roughly eight days since being ousted from the White House.

Appearing in New York City at a conservative think tank lunch event on Wednesday, Bolton took shots at his former boss's foreign policy decisions.

He said Trump's invitation to Taliban leaders to meet at Camp David days before before the 18th anniversary of the 9/11 attacks sent a "terrible signal" and was "disrespectful" to the victims because the group provided sanctuary to al Qaeda, according to Politico.

That meeting was canceled and Trump declared negotiations over an American withdrawal from Afghanistan “dead" after the Taliban claimed responsibility for a bombing in Kabul killed an American soldier and others.

Bolton brought up Iran and North Korea, saying any attempts to negotiate with them were "doomed to failure." He also complained that a scrapped military response to Iran after it shot down a U.S. drone in June emboldened Tehran to go through with weekend drone attacks on the Saudi oil industry.

The United States did slap new sanctions on Iran a couple day later, although Trump said they were planned prior to the drone being shot down. The following month the U.S. shot down an Iranian drone in the Strait of Hormuz. Iran denied it lost any drones in the area.

One source in the room said Bolton "ripped Trump, without using his name, several times" at the event attended by Gatestone Institute donors. High-profile attendees included billionaire Rebekah Mercer, lawyer Alan Dershowitz, and former Attorney General Michael Mukasey.

A rift had long been growing between Trump and the hawkish Bolton when the president announced his third national security adviser's departure last week. Trump tweeted that he "disagreed strongly with many of his suggestions, as did others in the Administration."

Trump announced Wednesday that Robert O'Brien, the special presidential envoy for hostage affairs at the State Department, would be his next national security adviser.