In four hours of evidence to Britain's inquiry on Iraq, a somber Brown repeatedly expressed regret over the lost lives of soldiers and civilians, and acknowledged mistakes were made by leaders in Washington and London.

Brown, who served as Treasury chief from 1997 to 2007 and approved military spending, dismissed claims he had choked Britain's defense budgets or allowed soldiers to go to war without adequate equipment.

Defending his role in the conflict, but cautious not to inflame tensions over the unpopular war ahead of a looming national election campaign, Brown said joining the 2003 US-led invasion was a tough call.

“We have got to recognize that war may be necessary, but it is also tragic in the effect it has on people's lives,” said Brown, who voted - like a majority of British lawmakers - to approve Britain's role in the war.

“These were difficult decisions ... ,” Brown said. “I believe they were the right decisions for the right reasons.” But he was critical of US planning, saying American officials failed to heed warnings about the need for clarity on how to protect and govern Iraq in the aftermath of the invasion.

“It was one of my regrets that I wasn't able to be more successful in pushing the Americans on this issue - that the planning for reconstruction was essential, just the same as planning for the war,” Brown said. He said he'd drafted a paper listing British reconstruction plans and sent it to the US government in early March 2003.

The inquiry is Britain's third and widest-ranging examination of the conflict, which triggered huge protests and left 179 British troops dead before the country's forces withdrew from Iraq last year. The inquiry won't apportion blame or establish liability, but will offer recommendations later this year on how to prevent errors in the future.