Islamabad, Washington's key ally in the fight against Al-Qaeda and Taliban militants, is believed to have about 50 nuclear-armed weapons or warheads, an arsenal it began assembling after successfully carrying out its first nuclear tests in May 1998.

There is no evidence that any of the weapons, said to be spread out in various locations around the country, currently are at risk.

But the volatile political climate following a move last week by President Pervez Musharraf to call a state of emergency has led anxious US officials to be more vigilant.

"I have learned that we don't have as a strong handle on it as I thought we do," said US Democratic Representative Ellen Tauscher, after being briefed in Congress this week on the state of the Pakistan nuclear program.

"We need a lot more visibility on what's going on in Pakistan," the Democratic lawmaker said.

"They have nuclear weapons and it is such a volatile part of the world."

 Source : Spacewars.com