The former chief strategist to US President Donald Trump has vowed to "go to war" for the president’s agenda after being sacked from office.

Steve Bannon told Bloomberg in an interview on Friday that he is prepared to fight the same fights, just from outside the White House.

"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 said.

On Friday, Trump's Press Secretary Sarah Sanders issued a statement saying, "White House Chief of Staff John Kelly and Steve Bannon have mutually agreed today would be Steve's last day."

“We are grateful for his service and wish him the best,” Sanders stated.

Bannon’s expulsion is said to have been resulted from an interview that infuriated the US president last week in which had claimed to have the power to fire officials at the State Department and contradicted Trump on North Korea.

The 63-year-old strategist was labeled as a white supremacist as he was formerly the executive chairman of the far-right news outlet Breibart, an online news website which many believe publishes racist and anti-Semitic articles.

Additionally, Trump was reportedly suspicious of Bannon as the man behind the many leaks that have driven the White House into chaos.

Trump has long denounced leaks of sensitive information to media, including the details of his confidential Oval Office phone conversations with other world leader as well as other White House secrets.

“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,” he emphasized.