LONDON — Britain cannot defeat terrorism unless moderate Muslims do more to confront militancy in their own communities, Prime Minister Tony Blair said Tuesday.

Blair said the vast majority of Muslims abhorred terrorism and wanted to defeat it, but said they had to do more to counter what he described as the extremists' misplaced anger and grievances.

Moderates, he said, must "stand up against the ideas of these people, not just their methods."

"If you want to defeat this extremism, you've got to defeat its ideas and you've got to defeat in part a completely false sense of grievance against the West," said Blair, testifying before a House of Commons committee. "The government has its role to play in this, but honestly, the government itself is not going to defeat this."

Shortly after the July 7, 2005, attacks on London, Blair pledged that officials would work with Britain's 1.5 million Muslims to fight the militant ideologies that are seducing a minority of young people like the four who carried out the attacks.