"There have been 7,000 madrassas built along that border.... that's where bin Laden lives and we will go at him if we have actually intelligence," he added

Paulin too agreed that a nuclear Iran or an unstable Pakistan were "both extremely dangerous" but said even al Qaeda had declared Iraq as the central front in the war on terror.

In the Friday debate, Obama said Pakistan had failed to take strong action against militants despite the billions of dollars from the US after the 9/11 terrorist attacks.

"They have not done what needs to be done to get rid of those safe havens," Obama said. "If the United States has al-Qaida, bin Laden, top-level lieutenants in our sights, and Pakistan is unable or unwilling to act, then we should take them out."

McCain, however, was less aggressive. "You don't do that. You don't say that out loud. If you have to do things, you have to do things, and you work with the Pakistani government," the 72-year-old Vietnam veteran said.