Sir John Chilcott, far right, arrives with Britain's Lord Butler, second right, and the team, left to right, Ann Taylor, Michael Mates and Lord Inge for a news conference in London on July 14, 2004 to release their report on Britain's pre-war intelligence about Iraq's weaponry. (Matthew Fearn/Reuters)

Britain was to begin a long-awaited inquiry in London Thursday into mistakes made before and during the Iraq war.

The independent inquiry is expected to look into the Sept. 11, 2001, attacks on the United States, the 2003 invasion of Iraq and problems with post-war reconstruction.

Current and former British ministers, such as ex-prime minister Tony Blair as well as foreign officials, including U.S. government staff, may be called to testify before the inquiry.

Sir John Chilcott, a former senior civil servant who will head the yearlong inquiry, was meeting with his team Thursday to decide on guidelines governing it.

The British military formally ended combat operations in Iraq on April 30 after six years by handing over control of its main base in Basra to an American brigade.