The United States has helped Pakistan improve security arrangements for its nuclear arms and is "comfortable" the weapons are secure, US defence secretary Robert Gates said in an interview aired on Sunday.
The Pakistani government has come under repeated attack from Taliban extremists, most recently on Friday when two suicide bombers eluded security and blew themselves up in a mosque in Rawalpindi, home to the country's military establishment, killing some 40 people.
The attack raised concerns about how the bombers penetrated what should have been one of the country's most secure areas. In light of the blasts, Gates faced questions about the security of Pakistan's nuclear arms.
"We are comfortable with the security of their weapons," he told CBS's 'Face the Nation' programme.
Asked how he could be sure, given reports the United States does not know where all the arms are located, Gates would only say that based on the information available, US officials were comfortable with their safety.
"We have a good relationship with them. We've actually given them assistance in improving some of their security arrangements over the past number of years. This is not a new relationship. And I think just based on the information available to us that gives us the comfort," he said.
Pakistan, which has not signed the nuclear Non-Proliferation Treaty, conducted several nuclear tests in 1998. The country is estimated to have at least 60 nuclear warheads, possibly stored in component form, according to a US Congressional Research Service report in October.
Concern about nuclear safety in the wake of the September 11, 2001 attacks on New York and Washington prompted former Pakistani president Pervez Musharraf to have the country's nuclear arsenal moved to six secret locations, the report said, citing press reports.
Proliferation is a concern with Pakistan. The father of the country's nuclear programme, AQ Khan, was involved in supplying North Korea, Iran and Libya with materials related to uranium enrichment, the report said, and al Qaeda leader Osama bin Laden reportedly has tried to make contact with the network.
