Steve Bannon is out as White House chief strategist, and returning to Breitbart News.

"White House Chief of Staff John Kelly and Steve Bannon have mutually agreed today would be Steve's last day," White House Press Secretary Sarah Huckabee Sanders said in a Friday statement. "We are grateful for his service and wish him the best."

He has returned to Breitbart News, where he was formerly the chairman, according to the publication. And Bannon told Bloomberg News he's "going to war" for his old boss, the commander-in-chief.

Get Breaking News Delivered to Your Inbox

"If there's any confusion out there, let me clear it up: I'm leaving the White House and going to war for Trump against his opponents -- on Capitol Hill, in the media, and in corporate America," Bannon told the outlet.

Mr. Trump and senior officials at the White House have been debating when to get rid of Bannon and how, the New York Times said, according to two administration officials. A person close to Bannon said him leaving was his idea, that report said, and that he had actually submitted his resignation to Mr. Trump on Aug. 7. The report added that his departure was supposed to be revealed publicly at the beginning of the week, but the events in Charlottesville, Virginia, forced the White House to hold off.

The announcement comes days after sources told CBS News that chief strategist's job was in serious jeopardy.

But Bannon's confidence in the presidency seems to be lost, according to an interview he gave the Weekly Standard on Friday.

"The Trump presidency that we fought for, and won, is over," Bannon told the Weekly Standard. "We still have a huge movement, and we will make something of this Trump presidency. But that presidency is over. It'll be something else. And there'll be all kinds of fights, and there'll be good days and bad days, but that presidency is over."

At his press conference at Trump Tower earlier this week, Mr. Trump was asked if he has confidence in Bannon.

"Well, we'll see… Look, look, I like Mr. Bannon," Mr. Trump said. "He is a friend of mine. Mr. Bannon came on very late. You know that. I went through 17 senators, governors and I won all the primaries. Mr. Bannon came on very much later than that. And I like him. He is a good man. He is not a racist. I can tell you that. He is a good person. He actually gets a very unfair press in that regard. We'll see what happens with Mr. Bannon. He is a good person and I think the press treats him frankly very unfairly."

Bannon is the latest senior official to exit the White House, as the president's rhetoric draws bipartisan criticism and his approval ratings decline.

Last month, Reince Priebus left his post as chief of staff, and Sean Spicer departed his job as press secretary. Priebus was replaced by Department of Homeland Security Secretary John Kelly, and Sarah Huckabee Sanders replaced Spicer. On Kelly's first day on the job, Anthony Scaramucci, who was the communications director for one week, also departed.

Bannon represented a more nationalist and populist faction of the White House.

Bannon lashed out at his rivals in the administration this week, telling progressive American Prospect writer Robert Kuttner about his plan to neutralize his opponents, including top officials and adviser to Mr. Trump

"They're wetting themselves," he said of his adversaries in the administration who disagree with him on trade and economic policies.

Bannon also told the American Prospect he wants to create an outside group of trade hawks with factions from both the left and the right sides of the political spectrum.

He also openly contradicted Mr. Trump's North Korea strategy. The president has been clear the U.S. is "locked and loaded" and ready to intervene against North Korea if necessary, but Bannon said a military option will never work on the Korean Peninsula.

"Until somebody solves the part of the equation that shows me that 10 million people in Seoul don't die in the first 30 minutes from conventional weapons, I don't know what you're talking about, there's no military solution here, they got us," Bannon said.

House Minority Leader Nancy Pelosi responded to Bannon's departure.

"Steve Bannon's firing is welcome news, but it doesn't disguise where President Trump himself stands on white supremacists and the bigoted beliefs they advance," Pelosi said in a statement.

"President Trump's growing record of repulsive statements is matched by his repulsive policies. Personnel changes are worthless so long as President Trump continues to advance policies that disgrace our cherished American values. The Trump administration must not only purge itself of the remaining white supremacists on staff, but abandon the bigoted ideology that clearly governs its decisions."

This is a developing story. Check here for live updates.

CBS News' Rebecca Shabad and Kathryn Watson contributed to this report.