A US nuclear expert says Islamabad is continuing to expand its nuclear bomb-making facilities amid concerns over its nukes' security.

David Albright, a former senior weapons inspector for the UN's International Atomic Energy Agency in Iraq, said satellite images showed two plutonium-producing reactors were nearing completion at Pakistan's Khushab's nuclear facility, Britain's Observer newspaper reported on Sunday.

"In the current climate, with Pakistan's leadership under duress from daily acts of violence by insurgent Taliban forces and organized political opposition, the security of any nuclear material produced in these reactors is in question," Albright said in a report issued by the Institute for Science and International Security (ISIS) in Washington.

Khushab is a rural district located in the Punjab Province about 258 km (160 miles) south-west of the capital, Islamabad. The reactors in Khushab are situated on the border of Punjab and the North-West Frontier Province, the scene of heavy fighting between Taliban militants and Pakistani troops.

Taliban have pushed towards Islamabad and other major cities across nuclear-armed Pakistan.

Last week, the US Secretary of State, Hillary Rodham Clinton, said in an interview that the US was worried about the 'unthinkable' in Pakistan - that the Taliban and al-Qaeda could topple the government, giving them 'the keys to nuclear arsenal'.

Pakistan has dismissed US concerns, saying its armed forces have full control over the country's nuclear installations.

Albright warned that Pakistan's atomic weapons program could also trigger a renewed nuclear arms race with its arch rival India in the troubled South Asian region.

In a show of force, both countries tested a number of nuclear weapons in 1998, and both are thought to have nuclear missiles and aircraft capable of delivering such weapons. India first tested a nuclear 'device' in 1974.

India and Pakistan have refused to sign the nuclear Non-Proliferation Treaty (NPT) and other treaties that restrict developing nuclear weapons.

JR/AAM/MMA