Former White House chief strategist Stephen Bannon said that it would be concerning if President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE had previous knowledge about a 2016 Trump Tower meeting between campaign officials and a Russian lawyer.

Bannon initially told MSNBC’s Ari Melber on Friday that he didn’t believe that Trump had engaged in “treasonous behavior” because it “hasn’t been proven that he knew anything about it.”

Melber then noted that Bannon has previously said that “there’s zero chance” that Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE didn’t tell the president about the meeting.

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“If a candidate knows about that in advance, then are they a part of treasonous behavior by your standard?” the MSNBC host asked.

“I think you have to call into question,” Bannon replied. “If somebody is actually out there trying to get information from foreign parties, you have to question it, yeah.”

“So if Mueller could prove that about Donald Trump, that would concern you,” Melber said.

“It would definitely concern me, yes,” Bannon said. “But the president has been pretty adamant that he didn’t know it and hasn’t known about it.”

CNN reported last month that Trump's former longtime personal attorney Michael Cohen is prepared to tell special counsel Robert Mueller that Trump had approved the Trump Tower meeting.

The former White House chief strategist came under fire from the Trump administration last year after it was revealed that he called the meeting between Trump Jr. and a Russian lawyer “treasonous.”

“The three senior guys in the campaign thought it was a good idea to meet with a foreign government inside Trump Tower in the conference room on the 25th floor — with no lawyers. They didn’t have any lawyers,” Bannon told “Fire and Fury: Inside the Trump White House” author Michael Wolff.

“Even if you thought that this was not treasonous, or unpatriotic, or bad shit, and I happen to think it’s all of that, you should have called the FBI immediately," Bannon said in the book.

The president responded by claiming that Bannon had “lost his mind."

Bannon later said that his comments were in reference to former Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE, not Trump Jr.