The United States says new efforts are being made to resolve the fate of hundreds of thousands of soldiers from all sides in the Vietnam War, who are still listed as missing in action.

An official in Washington -- a deputy assistant defence secretary, Bob Jones -- said Vietnam would be given unprecedented access to American military records, to help identify the burial sites of Vietnamese military casualties.

And Laos and Cambodia were being invited to join discussions about giving improved access to investigators.

The latest moves follow what the official called significant improvements in the level of help from Vietnam over the past year.