Even if the number two al Qaeda leader were captured in an offensive by Pakistani forces it would not end the threat from Osama bin Laden's world-wide organisation, senior US officials said on Friday.
"There is no silver bullet to disbanding al Qaeda," President George W. Bush's national security adviser Condoleezza Rice told CNN.
Rice and General Richard Myers, head of the US military joint chiefs of staff, expressed caution about reports that Pakistani troops had Ayman al-Zawahiri, bin Laden's right-hand man, trapped in military action on the Afghan border.
If Zawahiri were captured, Myers said on CNN, "It's one step in a many-step process to defeat international terrorism. By itself, it's not going to stop plots that are already under way ... but when you take the head off an organisation, it's obviously going to have an impact."
He added, "Certainly if you capture someone like al-Zawahiri that would be good news, because presumably he knows where (bin Laden) is or where he was, and if he talks or if he is captured with documents or other material you could find out where some of the other leadership is, absolutely."
Pakistani leaders have said they believe a "high-value target" is among the al Qaeda fighters who are now engaged in a fierce battle, but US officials stress they do not yet know the identity of the person.
Myers said the clash in the South Waziristan area of Pakistan was a Pakistani operation, with coalition forces providing support from across the Afghan border.
Rice stressed it was not known who was among the group of trapped al Qaeda fighters. "I don't think we know whether Zawahiri is indeed in that area and pinned down or not. First reports are often wrong," she said on CBS.
"I have to caution that, as we've always said, al Qaeda is not just one man, it's a network. And we've already captured or killed two-thirds of their known leadership, their kind of field generals, the people who plot and plan their attacks."
She said, "Obviously when you can kill or capture one of the major leaders, and Zawahiri is clearly one of their major leaders, it would be a boost in the war on terrorism. But I don't think we should jump to the conclusion that it would by any means completely disable al Qaeda."
OSAMA'S ARREST: WOLFOWITZ: The capture of al Qaeda chief Osama bin Laden would be "very big" but would not crush highly decentralised terror networks, US Deputy Defence Secretary Paul Wolfowitz said in Washington on Thursday.
"Obviously getting bin Laden would be a very big thing, but anyone who thinks that that's going to be the end of al Qaeda - the end of these terrorist networks - doesn't understand how they work," he said in an interview with the Public Broadcasting System.