Treasury chief Gordon Brown on Friday launched his campaign to become Britain's next prime minister and win back voters disenchanted after a decade of Labour Party rule.

Brown said his government would honor Britain's commitments in Iraq but acknowledged mistakes had been made, and he pledged that his government would be more open and cooperate more with Parliament.

"We will keep our obligations to the Iraqi people. These are obligations that are part of U.N. resolution, they are in support of a democracy."

He said he would be talking to Iraqi government officials and British forces in the country.

"I do think that over the next few months the emphasis will shift. We've got to concentrate more on political reconciliation in Iraq. We've got to concentrate more on economic development so that people in Iraq ... feel that they have a stake in the country for the future," Brown said.

Britain ranks second, after the United States, in terms of troops committed to Iraq. The British total is 7,100 but a reduction to 5,000 is planned for later in the year.

President Bush seemed optimistic Thursday about the possibility of continuity on Iraq between Prime Minister Tony Blair and his likely successor.

The president told reporters that he believes Brown "understands the consequences of failure" in Iraq. As Bush sees it, a U.S. defeat would give a boost to terrorism.

Blair, who is stepping down on June 27, formally endorsed Brown shortly before the Treasury chief began a series of appearances Friday.

"He has a quite extraordinary and rare ability, a tremendous talent to be put at the service of our country," Blair said of Brown, who faces no serious opposition in his bid for promotion.

"He has shown in his exemplary management of the economy ... that he has the strength, judgment and experience to make a great prime minister," Blair said.

Often described as dour, the 56-year-old Brown has been accused of "Stalinist ruthlessness" and a lack of people skills.

Former Cabinet Minister Charles Clarke last year called him a "control freak." Andrew Turnbull, Britain's former top civil servant who broke a customary code of silence, said Brown has often belittled colleagues.

"I don't think we'll see true Brown until the general elections," which are not expected before 2009, said Anthony Seldon, a biographer who followed Blair and Brown.

The general elections will pit Brown, a rumpled intellect, against David Cameron, the fresh-faced Conservative Party leader who has been compared to the younger charismatic Blair.

Both Brown and Blair won their House of Commons seats in 1983. It was the beginning of a partnership and a long and often bitter rivalry.

They shared an office, and when Labour Party leader John Smith died in 1994, both men thought about standing in the ensuing leadership election.

Political lore has it that the two struck a deal at a London eatery, that Blair would be party leader and Brown would run the Treasury until the middle of a second term when Blair would step down, clearing the way for Brown.

That didn't happen, and as the years passed British newspapers became saturated with rumors of squabbles between the two men.

While Blair initially supported the notion that Britain could embrace the common European currency — the euro — Brown quickly shot down the idea, establishing a multifaceted test to show that the British economy would surely suffer. Needing Brown's backing, Blair dropped the notion.

Brown stuck to Labour's 1997 pledge to freeze income tax rates, and increased government spending. He also pushed for the Bank of England's independence, credited for Britain's steady economic boom since World War II.

"I think people will look back on this political partnership and the relationship between me and the prime minister and say, 'well, it is completely unique and you've had a chancellor and prime minister who have worked together,"' Brown said recently.

Brown's political ambition surfaced when he was 12, when he started canvassing for the Labour Party.

He gained a doctorate from Edinburgh University, in Scotland, having written his thesis on the links between the Labour Party and Scottish trade unions, according to Robert Peston, author of the 2005 book "Brown's Britain."

But beyond his loyalty to Labour, little is known about Brown's political leanings. He has close ties to the U.S. Democratic Party, and was said to have been particularly close to Massachusetts Sen. John Kerry. President Bush said Brown was "an open and engaging person."

"And I found him to be an easy-to-talk-to, good thinker," Bush said Thursday.