TAYLOR, Michigan — President Bush, who will be hailed at his party's national convention this week as a great wartime leader, said in an interview aired Monday that the war on terror cannot be won.

"I don't think you can win it, but I think you can create conditions so that those who use terror as a tool are less acceptable in parts of the world," Bush told NBC's "Today" show. "Let's put it that way. I have a two-prong strategy. On the one hand, it's to find them before they hurt us. And that's necessary. I'm telling you. It's necessary."

Bush said that part of the effort is going well. "I mean, we are dismantling al-Qaida as we knew it," he said.

The second part of the strategy, Bush said, "is to spread freedom and liberty." He declined to predict when the war against terror might end.

"When we succeed in Iraq and Afghanistan it's the beginning of the end for these extremists because freedom is going to have a powerful influence to make sure your kids can grow up in a peaceful world," he said.

White House spokesman Scott McClellan said Monday that Bush was talking about winning the war "in the conventional sense."

"I don't think you can expect that there will ever be a formal surrender or a treaty signed like we have in wars past," McClellan said aboard Air Force One as Bush headed to a New Hampshire campaign event. "That's what he was talking about when he was talking about that. It requires a generational commitment to win this war on terrorism."

"You can't put a time frame on it, per se," McClellan said.

The Democrats pounced quickly on Bush's remarks.

"After months of listening to the Republicans base their campaign on their singular ability to win the war on terror, the president now says we can't win the war on terrorism," said vice presidential candidate John Edwards. "This is no time to declare defeat. It won't be easy and it won't be quick, but we have a comprehensive plan to make America safer. And that's a difference."

Edwards also criticized a Bush comment to Time magazine in which the president termed the swift victory in Iraq a "catastrophic success."

"Had we to do it over again, we would look at the consequences of catastrophic success — being so successful, so fast, that an enemy that should have surrendered or been done in escaped and lived to fight another day," Bush told the magazine.

Said Edwards, "President Bush now says his Iraq policy is a catastrophic success. He's half right. It was catastrophic to rush to war without a plan to win the peace."