US President Joe Biden will formally apologise to the Native American community for the atrocities of a 150 year Indian boarding school policy that aimed to culturally assimilate indigenous children.

The US president is scheduled to issue the apology from Arizona on Friday.

"I'm heading to do something that should have been done a long time ago - make a formal apology to the Indian nations for the way we treated their children for so many years, " Biden told reporters on Thursday.

The federal government established Indian boarding schools from 1819 through the 1970s that forcibly removed children from their homes and families.

The boarding schools stripped indigenous children of their heritage and tried to assimilate Alaska Native, American Indian and Native Hawaiian children into white American culture.

There were more than 523 government-funded Indian boarding schools throughout the US in the 19th and 20th Centuries. Many of these schools were run by churches.

Tens of thousands of children were forcibly abducted by the government and sent to schools far from their homes. Indigenous children often faced emotional and physical abuse, including being beaten and starved when speaking their native languages.

In some cases, children died and never returned home.

Under the Biden administration, the US Department of Interior launched its first-ever federal investigation of the Indian boarding school system to address its painful history.

Interior Secretary Deb Haaland, the first Native American to serve as a cabinet secretary, led a "Road to Healing" tour in 2023 to speak with indigenous survivors.

The Department of Interior also launched an oral history project to document the experience of survivors.

Biden's apology comes less than two weeks before the presidential election.

He is scheduled to deliver the announcement at the tribally-controlled Gila Crossing Community School outside of Phoenix, the Washington Post reported.

It marks the first time a US president will address the suffering of indigenous children from the boarding school system.

In Canada, which had a similar policy in place, the prime minister apologised in 2008 for forcing about 150,000 indigenous children to attend state-funded Christian boarding schools.

The government also launched a truth and reconciliation commission that documented the history of the country's residential school system.