AUSTRALIA and other countries that took part in the Iraq invasion

AUSTRALIA and other countries that took part in the Iraq invasion could be asked to help a new British inquiry get to the bottom of why the war went ahead.

The head of the long-awaited inquiry, former civil servant John Chilcot, said last night he and his four fellow panel members would be interested in talking to officials from a range of countries that backed the US-led invasion.

However, if any member of the Howard government, which sent hundreds of troops to Iraq, agreed to co-operate with the inquiry, they would not be compelled to give evidence.

"I don't rule out discussions with key international figures, figures from other countries insofar as they are willing to have discussions with us," Sir John said as he began outlining the terms of reference for the inquiry.

"I am very conscious of the fact that the Iraq conflict on the side of the West was an alliance with a number of members from different countries.

"They, too, will have been seeking to learn lessons and we shall need to take into account as best we can any conclusions they find or are in the process of forming.

"(But) discussions and evidence sessions aren't necessarily the same thing and, of course, we have no power to compel witnesses here let alone people in foreign governments."

Former British prime minister Tony Blair, who controversially agreed to join the US for the 2003 Iraq invasion, will be one of the star witnesses to be asked to appear before the panel made up of privy councillors.

The inquiry will examine the years between the northern summer of 2001 and July this year, including the lead-up to the conflict, the military action taken by Britain and its allies and the aftermath.

A key focus will be on the decisions made by Mr Blair and his fellow ministers and senior government officials to take part in the war and why.

Sir John vowed the inquiry would be open and transparent and would not shy away from criticising the British government if warranted.

"If we find ... that people fell short in their duty, made mistakes, acted wrongly, we shall most certainly say so," he said.

"The inquiry is not a court of law and nobody is on trial. But I want to make something absolutely clear -- the committee will not shy away from making criticism."

The inquiry was announced by Prime Minister Gordon Brown last month, honouring a pledge that the run-up to and conduct of the US-led and British-backed conflict would be examined once British troops pulled out.