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The man who hopes to succeed Prime Minister Tony Blair laid out a centrist vision for Britain on Monday in a speech that was crucial to his bid for a job he has coveted for years.

Treasury chief Gordon Brown praised Blair effusively in a closely watched address to the governing Labour Party's annual conference, saying he regretted the bitter infighting that recently roiled the party. Blair led a standing ovation as he finished.

Appearing assured and impassioned, Brown signaled he would stick to Blair's strategy of seeking to appeal to moderate Britons but he also tried to assuage concerns on the party's left.

He said Blair had been right to realize that no one can be neutral in the war on terrorism.

"Tony, you taught us something else, and once again you saw it right," Brown said. "The world did change after Sept. 11 ... and we, Britain, have new responsibilities to discharge."

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Brown said Labour must never succumb to anti-Americanism but he gave a wink to the party's strong opposition to Blair's decision to join the U.S.-led attack on Iraq, saying Parliament — not just the prime minister — should have the power to declare war.

He promised to renew the party "not just holding the center ground, but modernizing it in a progressive way too."

Some delegates said Brown had delivered in a speech that many were looking to for hints of what kind of prime minister he would be.

"I was skeptical" about whether he'd be a good leader, said John Thackway, 70, a Labour member for more than 50 years. "But he made a great speech. I was not committed, but now I would vote for him."

The applause was loudest when Brown spoke about domestic policies, and his assertion that he would "relish" the chance to take on the resurgent Conservative Party was greeted with the loudest cheer of the speech.

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Brown acknowledged there had been ups and downs in his long political relationship with Blair.

"Where ... differences have been a distraction from what matters, I regret that and I know Tony does too," Brown told Labour's annual conference in Manchester.

He echoed Blair's call for Labour to stop obsessing about its internal politics and focus on policies that matter to Britons.

"The only reason any of us is here is that we are in politics as servants of the people," he said.

Brown, a deeply private man, tried to give Britons a glimpse of who he is and what drives him by recalling how strongly his parents shaped his view of the world.

His father, a minister, "told me 'You can leave your mark on the world for good or bad,'" Brown said. "My mother taught my brothers and I that whatever talents we had, we should try to use them to the full."