An independent inquiry into the reasons why Britain decided to join the U.S.-led invasion of Iraq in 2003 began Thursday.

Former British senior civil servant John Chilcot outlined the terms of reference for the inquiry and explained how his committee conducted the investigation.

Chilcot spoke after Prime Minister Gordon Brown was forced to abandon plans for the hearing to be held behind closed doors.

"We need to address different views over what happened in Iraq and why," Chilcot said. "The inquiry will consult a range of experts on military law and operations."

It was reported that former Prime Minister Tony Blair, who sent British troops into the conflict, will be called to testify.

The inquiry was expected to cover an eight-year period from summer 2001 to July 2009, including the invasion preparation and the intelligence used to justify it.

Also Wednesday, local media reported that two more British hostages in Iraq were believed to have been killed, leaving just one of five men kidnapped together in 2007 still unaccounted for.

Brown has appealed for the release of British hostage Peter Moore, an IT consultant, who was seized along with the four others in Baghdad.

Brown said the government recently told the families of hostages Alan McMenemy and Alec MacLachlan that the two were likely dead.

"I and the entire government are committed to doing everything that we can for the release of Peter Moore, whom we still believe to be alive," Brown said.

(Xinhua News Agency July 30, 2009)