The United States has formally apologised to American Indian tribes for "ill-conceived policies" and acts of violence against them.

Republican Senator Sam Brownback read the congressional resolution at an event attended by representatives of five Indian nations at the Congressional Cemetery in Washington: the Cherokee, Choctaw, Muscogee (Creek), Sisseton Wahpeton Oyate and Pawnee nations.

Four of the five are based in Oklahoma and the Sisseton Wahpeton Oyate are in South Dakota.

The Cherokee originally were from the south-eastern United States but were forced to migrate to Oklahoma in the early 1800s.

Chad Smith, chief of the Cherokee Nation, said most tribes had not specifically asked for a formal apology from the US government, but the gesture was appreciated.

"It's difficult to issue an apology and sometimes it's difficult to accept one," Mr Smith said.

"Once you put those differences of the past aside, perhaps the next step is, can you do any better in this round?

That is where our greatest challenge is. The history of the US (toward American Indians) is not a bright record. The real question is, what happens from this day forward?"