A final ruling on whether to overturn Facebook's ban on former US president Donald Trump will take a bit longer than anticipated, an independent oversight board said on Friday.

Critics of the social media company and even strong advocates of unfettered political discourse called on Facebook's oversight board to endorse the decision to boot Trump from the platform in the aftermath of the January 6 attack on the US Capitol.

"The board's commitment to carefully reviewing all comments has extended the case timeline," a spokesperson told AFP.

"The board will announce its decision on the case concerning former US President Trump's indefinite suspension from Facebook and Instagram in the coming weeks."

The Facebook oversight board had originally expected to have its decision by this month.

Calling Trump a "clear and present danger," scholars and civil rights advocates have urged Facebook to permanently ban the former US president from the platform.

Conservatives on Capitol Hill and beyond have contended that moves by Facebook and Twitter to "deplatform" Trump demonstrate political bias and inhibit free speech.

An extended public comment period ended in February with more than 9,000 submissions regarding the case, according to the board.

The social network itself asked the independent body to review Trump's eviction from the online community.

The oversight board has the final say on what is removed or allowed to remain on the world's biggest social network.

Trump's access to social media platforms that he used as a megaphone during his presidency has been largely cut off since a violent mob of his supporters stormed the Capitol in Washington.