The Joint Chief of US Staff Admiral Mike Mullen, who had visited New Delhi soon after the Mumbai attacks, was addressing a conference in Washington on "Global Trends and Security" on Thursday, organised by the Princeton University.
"I was struck in those attacks by what 10 terrorists could do to two nuclear-armed countries," he said.
Mullen said it is a different kind of terrorism. "It wasn't blowing up a building. It wasn't Madrid. It wasn't London or New York or the embassies," Mullen said.
The admiral said the al Qaeda is still in Afghanistan and Pakistan, although it is greatly diminished. In Afghanistan, he said, the violence has got worse.
"We need to see the governance develop in Afghanistan. We need to improve our security there, security for the people," he said.