LONDON - Prime Minister Gordon Brown made a long-awaited appearance on Friday before a high-level inquiry into the Iraq war, defending the Labour government's decision to invade alongside U.S. troops but questioning United States planning for the aftermath.

“;I believe this is the gravest decision of all, to make a decision to go to war,”; Brown said. “;It was the right decision made for the right reasons.”;

Addressing a panel of four knights and a peer in the Queen Elizabeth II Conference Center in London, Brown offered veiled criticism of the preparations to rebuild Iraq after the invasion, when the country descended into lawlessness, terrorism and sectarian strife.

“;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,”; he said.

The hearing was billed as a defining opportunity for Britain to get some answers on the war from Brown, who as finance minister was the most senior member in the Cabinet of his predecessor, Tony Blair. But he kept an even keel and dodged the type of knockout blow that could have hurt him in the national elections widely believed to be coming in May. He reaffirmed the rationale for entering the war while taking care to pay respects repeatedly to the dead and rebuffing critics who accused the Treasury of underfinancing the military during the war.

After his final statement, Brown let loose with a rare public smile, apparently sending a message that he had nothing to hide and had done nothing to apologize for. As he walked out the front door of the conference center, he took care to shake the hand of a security guard - a marked contrast to an embarrassing moment a year ago when he failed to shake hands, as President Barack Obama had, with a guard at the door of 10 Downing St. His appearance also contrasted sharply with that of Blair, who entered the building in secret during his hearing this year to avoid the many protesters who blamed him for Britain's involvement in the war.

For much of Blair's decade in office, he and Brown were bitter rivals, with Brown pressing for Blair's job. But, referring to the question of Blair's behavior in the months leading to the war - when many Britons suspected that Blair had given private assurances of British support to President George W. Bush - Brown said Friday, “;Everything Blair did, he did properly.”;

A direct, pragmatic man who is uncomfortable showing any sign of emotion in public, Brown swatted away attempts by questioners to learn about his deepest thoughts at the time.

Unlike his predecessor, Brown did not attach a high moral imperative to the war, sticking stubbornly to his main thesis that Saddam Hussein's refusal to comply with U.N. sanctions justified the campaign.

“;After 14 resolutions, the diplomatic channels had been exhausted,”; he said.

Pressed to explain his influence on Blair, who has been widely criticized here for being unconditional in his support of American war planning, Brown said that his role was to look after the money, not to second-guess the prime minister.