Washington was keeping a close eye on Pakistan's nuclear arsenal following the recent upheaval, said Lieutenant General Carter Ham, Director of Operations with the US Joint Chiefs of Staff.

"We will watch that very closely," he told reporters. "Any time there is a regime that has nuclear weapons and that experiences a situation like in Pakistan, of course there is a primary concern."

Former Pakistan prime minister Benazir Bhutto said in an interview with the German daily Bild Wednesday that she was worried about what would happen if extremists managed to win hold of the country's nuclear arsenal.

Pakistan has been a declared nuclear power since carrying out its first tests in May 1998, in a series of tit-for-tat tests with India.

General Ham on Wednesday stressed Pakistan's contribution to the war in Afghanistan, even though Washington is currently reviewing its aid program to Islamabad.

"Pakistan has been a great partner so far on the war on terror cooperation along the border between Pakistan and Afghanistan. We certainly do not want to see that jeopardized," he said.

"Secondly, US and other forces in Afghanistan receive most of their supplies through and over Pakistan. Well over half of the supplies for forces in Afghanistan come through or over Pakistan," he added.

"From an operational standpoint, those are the two most significant concerns. I am confident that those aspects will be part of that review."

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