US President Joe Biden has formally apologized to the Native American community for a 150-year-old Indian boarding school policy aimed at the cultural assimilation of indigenous children, calling it a “sin on our souls”.

He said apologizing for the “stain on American history” was one of the most important things he did as president.

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

Ten days before the general election, Biden’s apology at an event in Arizona also gave him a chance to show his support for tribal nations in a swing state where the Democratic White House ticket won by just 10,000 votes in 2020.

“I formally apologize as president of the United States for what I did,” Biden said while visiting the tribally-controlled Gila Crossing Community School outside Phoenix. “It’s long overdue.”

The Biden administration says it has provided billions of dollars to support Native Americans, though affected communities say the president could do more.

Boarding schools stripped Native children of their heritage and attempted to assimilate Alaska Native, American Indian, and Native Hawaiian children into white American culture.

In the 19th and 20th centuries, there were over 523 government-funded Indian boarding schools in the US. 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 they spoke their native languages. In some cases, children died.

Under the Biden administration, the US Department of the Interior launched the first federal investigation into India’s boarding school system to address its history.

Interior Secretary Deb Haaland, the first Native American to serve as a cabinet secretary, toured last year to speak with indigenous survivors.

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

In Canada, which had a similar policy, the prime minister apologized in 2008 for forcing some 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.