A deadly weekend attack on Pakistan's army headquarters is causing concern about the security of nuclear weapons there.
A Taliban strike force killed 14 people and took dozens hostage in the attack.
Pakistani commandos ended the siege, but it raised questions about the safety of the country's arsenal.
Pakistan is thought to have between 70 and 90 nuclear weapons.
The missile sites are heavily guarded, and the warheads are electronically locked.
But some experts worry that the Taliban could forge ties with scientists at the site and get access to the weapons.