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British Prime Minister Tony Blair said Thursday he is stepping down on June 27, closing a decade of power in which he fostered peace in Northern Ireland, presided over an unprecedented period of prosperity and followed the United States to war in Iraq.

In a somber farewell, Blair moved to secure the party's future with a smooth transition to power. The British leader looked overcome with emotion, struggling to retain his trademark broad grin as loud cheers rang out.

"Hand on heart, I did what I thought was right," Blair told party workers and supporters at Trimdon Labour Club in his Sedgefield constituency in northern England. "I may have been wrong, but that's your call. But believe one thing if nothing else. I did what I thought was right for our country."

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Blair's earnest announcement, which lacked his usual slick spin, had been long expected. But he kept the timing a secret almost to the end.

In British parliamentary tradition, the leader of the largest party in the House of Commons serves as prime minister. Treasury chief Gordon Brown, Blair's partner in reforming the Labour Party and a sometimes impatient rival in government, was expected to easily win election as the party's new leader and become the next prime minister.

Blair has stopped just short of openly endorsing Brown, a stern Scot who has long coveted the top job. Last week, Blair said Brown would make "a great prime minister."

Blair embraced dozens of local activists as he arrived to greet around 250 supporters packed into the former mining village's Labour clubhouse. Some chanted "four more years," but were chided by the leader as he began his speech.

"That's not on message for today," Blair joked.

Deputy Prime Minister John Prescott announced right after Blair's speech that he, too, would resign.

The 54-year-old Blair saved his long-expected announcement until he returned to the district where he won election to Parliament in 1982, and where he announced in 1994 that he was a candidate to leader the Labour Party.

The announcement came days after Blair celebrated the 10th anniversary of Labour's landslide election victory of May 1, 1997.

Since then, he has been one of the most praised, and reviled, leaders in British history — the man who transformed the Labour Party, helped bring an end to Northern Ireland's Troubles but angered many of his supporters by committing Britain to a bloody, unpopular war in Iraq.

When he was elected at 43 in 1997, Blair was the youngest prime minister of the 20th century, the first born after World War II and the only one to have played in a college rock band, Ugly Rumours. He transformed Labour from an old-style social-democratic party to centrist "New Labour" and led it to three consecutive election victories.

Under the stewardship of Blair and Brown, the British economy has thrived — London rivals New York as the world's pre-eminent financial center, GDP is up, unemployment is down and interest rates are low, though rising. However, Blair's much-promised reforms to health and education remain incomplete, and soaring house prices and increasing personal debt threaten to widen the divide between the rich and poor.

Nonetheless, his supporters say Blair will be remembered for helping the poor.

"It's a nostalgic day but we're here to celebrate of all of Tony Blair's achievements, he's done so much to help the people of this country, and so much to lift people out of poverty," said Maureen Lenehan, an official at the Trimdon Labour Club.

Lenehan said she had met Blair on dozens of occasions since he became the local lawmaker, celebrating his 1997 election as prime minister at the small clubhouse.

"In the future he'll be able to come back here in his jeans and chat to the local people, just like he used to do when he was first elected," she said.

But despite his accomplishments — not least an end to three decades of violence in Northern Ireland — Blair's legacy looks to be dominated by Iraq.

His decision to stand shoulder-to-shoulder with U.S. President George W. Bush by committing troops to the invasion divided his party and the country. Blair said he was content for history to judge him, but four years on and with almost 150 British troops dead in Iraq, the war is more unpopular than ever.

His last months in office also have been overshadowed by a police investigation into claims his party and the opposition traded political honors for cash. Senior Blair aide Ruth Turner, Blair's chief fundraiser Lord Levy and two others have been arrested during the police inquiry into claims that seats in the House of Lords and other honors were awarded in exchange for party donation. Prosecutors are considering whether anyone should be charged.

Blair was questioned twice by police as a witness, although he is not considered a suspect.

In recent months, Blair's thoughts have turned to the lessons of his decade in power.

"When I first started in politics, I wanted to please everyone," Blair said during a tour of the Middle East in December. "After a time I learned that you can't please everyone, and you learn that the best thing is to do what you think is right and everyone can make their judgment."