A public inquiry into Britain's role in the Iraqi war has dedicated its first session to hearing evidence on UK foreign policy towards Iraq in the lead-up to the 2003 US-led invasion.

Leader of the Downing Street-appointed committee of former civil servants and advisers, Sir John Chilcot, opened the long-awaited probe on Tuesday with the promise not to "shy away from criticism".

Top officials from the Foreign Office and Ministry of Defense explained Britain's policy towards Iraq in 2001, two years before the invasion in March 2003.

Sir Peter Ricketts, a top intelligence official, told the Iraq inquiry that the UK government "distanced itself" from talks of removing Iraqi dictator Saddam Hussein in early 2001, and that it was assumed that it was not "our policy" despite growing talks in the US about the move.

"No-one is on trial here. We cannot determine guilt or innocence. Only a court can do that," Chilcot, who hopes to conclude his report in late 2010, said in his opening remarks, which he had previously made in response to opposition ministers' call for legal cross-examination of the officials on the key witness list.

"But I make a commitment here that once we get to our final report, we will not shy away from making criticisms, either of institutions or processes or individuals, where they are truly warranted," he added.

The most intensely expected highlight of the hearings will come from then prime minister Tony Blair, who led the country into the unpopular US-led invasion to oust Saddam despite huge public demonstrations against the campaign.

Blair will be called in January to give his evidence, with families of soldiers killed in the conflict urging for an insightful investigation.

Rose Gentle, whose 18-year-old son Gordon was killed in Iraq in 2004, is among the leading critics of the war.

"We do hope that the committee are going to be honest... I don't know why he (Gordon) died until the end of this inquiry," said Gentle, who co-founded Military Families Against The War.

She told the BBC that she was anticipating Blair's appearance to "ask him why he doesn't meet the families... if mistakes were made, he's the one that's got to live with it."

The bereaved families of some of the 179 British soldier killed in the six-year war, have also raised issues about whether they were properly equipped and trained.

Meanwhile, anti-war campaigners want the issue of the conflict's legality settled once and for all — as the war did not have an explicit approval from the UN Security Council.

On Tuesday, the inquiry also heard that the key turning point in discussions to oust Saddam came in the wake of the September 11, 2001 attacks.

ZHD/AKM