President Bush said Monday he was saddened by the loss of American lives in the battle in Afghanistan, but promised to keep the pressure on Al Qaeda until the terror organization is finally routed.

"History has called us to defend freedom," Bush said, responding to reporters' questions on the latest casualties in Afghanistan.

The president spoke hours after nine American soldiers died in a U.S.-led assault, eight of them when troops on two helicopters took enemy fire in the largest offensive of the five-month war against terrorists.

"I have said repeatedly, we are in a dangerous phase of this war," Bush said after a meeting with teachers to promote his education agenda.

"These are killers, these are murderers," the president said of the Al Qaeda and Taliban fighters.

Bush said he did not know the whereabouts of Al Qaeda leader Osama bin Laden or how many other top Al Qaeda figures might be in the area of the current combat.

"He's been awfully quiet ... I know there's no cave deep enough for Mr. bin Laden," he said.

"I am saddened by the loss of life," the president said. But he added, "I am just as determined now to fulfill this mission."