Adm. Mike Mullen, US President Barack Obama's top military adviser said Iran's objective is to obtain nuclear weapons - and that threatens the region.
Mullen said he's worried about Iran and about what US intelligence agencies don't know about the Teheran government. The chairman of the Joint Chiefs of Staff said the United States and its allies must work to engage Iran's leaders.
Mullen said there's a narrow window in which to work to block Iran from achieving nuclear capabilities.
Mullen appeared on ABC television's "This Week."