ANALYSIS - Pakistan's nuclear weapons are safe, for now

By Myra MacDonald

LONDON (Reuters) - Pakistan's nuclear installations are so well guarded that Islamist militants behind a wave of violence in the country's heartland would find it very hard to storm them and steal material for a nuclear bomb, analysts say.

But the sophistication of recent attacks and their proximity to Pakistan's nuclear infrastructure suggest this risk, while low, remains a cause for worry.

"I don't think it is realistic any more to say there is no threat to these weapons, that they are totally safe," said Professor Shaun Gregory at Britain's University of Bradford.

Heavy conventional guarding, a blanket of secrecy, deliberate deception, the separation of warheads from missiles, and security practices adopted from the United States are all used to protect weapons and nuclear installations.

The nightmare scenario would be of militants using a suicide bombing as a diversionary tactic in order to send in a team of commandos -- similar to those who attacked the Pakistan Army's own headquarters last month in the city of Rawalpindi.

Then, and given the secrecy surrounding Pakistan's nuclear programme this would need collusion and information from inside, they would try to grab fissile material for a nuclear bomb.

"If commandos managed to penetrate a nuclear installation, that would be a very serious breach," said Sharon Squassoni, at the Carnegie Endowment for International Peace in Washington.

"It's likely they would fail, it's very likely they would fail, but that would be a bit too close for comfort."