United States President Joe Biden will formally apologise for the government’s role in forcing Indigenous children into boarding schools where many were physically and sexually abused and nearly 1,000 died.

“I’m doing something I should have done a long time ago: to make a formal apology to the Indian nations for the way we treated their children for so many years,” Biden said as he left the White House on Thursday for Arizona.

Between 1869 and the 1960s, more than 18,000 Indigenous children — some as young as four — were forcibly taken from their families and put into the boarding school system.

The schools, often run by Christian churches, were part of the forced assimilation policy launched by Congress in 1819 as an effort to “civilise” Native Americans, Native Alaskans and Native Hawaiian peoples.

Children were beaten, sexually abused and banned from speaking their language and acting in any way that reflected their culture. Many didn’t see their families for years.

In a press release, the White House said Biden believes that “to usher in the next era of the Federal-Tribal relationships we need to fully acknowledge the harms of the past”.

His address on Friday will mark the first time a US president has apologised for the boarding school abuses and the forced removal of Indigenous children — something defined as an act of genocide by the United Nations.

Apology recommended

“I would never have guessed in a million years that something like this would happen,” said Interior Secretary Deb Haaland, a member of the Pueblo of Laguna nation in New Mexico.

“It’s a big deal to me. I’m sure it will be a big deal to all of Indian Country.”

Haaland is the first Native American to lead the Interior Department. She launched an investigation into the boarding school system shortly after being appointed. The department held listening sessions and gathered testimony from the survivors.

It documented nearly 1,000 deaths and 74 gravesites at more than 500 boarding school locations.

One of the recommendations of the final report was an acknowledgement of, and an apology for, the boarding school era. Haaland said she took that to Biden, who agreed that it was necessary.

Haaland will join Biden during his first diplomatic visit to a tribal nation as president, as he delivers his speech at the Gila River Indian Community, 48 kilometres (30 miles) south of Phoenix.

“It will be one of the high points of my entire life,” Haaland said.

The apology comes in the last weeks of the US presidential race as Vice President Kamala Harris’s campaign spends hundreds of millions of dollars on ads targeting Native American voters in battleground states including Arizona and North Carolina.

Canada has a similar history of subjugating Indigenous peoples and forcing their children into boarding schools for assimilation. Pope Francis issued a historic apology in 2022 for the Catholic Church’s cooperation with Canada’s “catastrophic” policy of Indigenous residential schools, saying the forced assimilation of Native people destroyed cultures, severed families and marginalised generations.

In 1993, President Bill Clinton signed a law apologising to Native Hawaiians for the overthrow of the Hawaiian monarchy a century earlier.