Pakistan is confident its nuclear assets will not fall into militant hands because it is constantly reviewing security and getting help from friendly countries, a senior defence official said on Sunday.

As Pakistan battles a Taliban insurgency, reports in the US media have raised the nightmare scenario of its nuclear weapons falling into militant hands.

'We are very confident,' Secretary of Defense Syed Athar Ali told Reuters in an interview on the sidelines of a security conference in Singapore. 'To talk of this falling into the wrong hands ... even the locations will not be known.'    

Ali did not name the countries helping Pakistan to ensure security. Last week, a source close to French President Nicolas Sarkozy said France and Pakistan are negotiating a partnership, including nuclear cooperation.

Nuclear security has been a question mark since Pakistani scientist Abdul Qadeer Khan, revered by many Pakistanis as the father of the country's nuclear bomb, confessed to selling nuclear secrets to Iran, North Korea and Libya in 2004.

US Defense Secretary Robert Gates, speaking at the conference on Saturday, gave a stern warning to North Korea after its nuclear test last week, saying it would be held accountable if it transferred any nuclear material outside its borders.

Pakistani forces have undertaken their most concerted offensive against an expanding Taliban insurgency that has raised fears for the nuclear-armed US ally's stability and the safety of its nuclear arsenal.

Military forces on Saturday regained full control of the main town in the Swat valley -- the focus of the recent offensive to dislodge thousands of Taliban fighters.   

Ali, a retired general, said the army would remain in Swat until the police took firm control after a military operation that he expected to wrap up in two to three days.

'They are almost at the verge of calling it off. Only two to three days of operations on some pockets of resistance and one odd spot which is very narrow,' Ali said.

He said if the militants move to other areas, then a political decision would be needed to extend the operation beyond Swat.

'If the terrorists and militants move to other sanctuaries and hideouts, then of course the threat will be assessed,' he said. 'Any further action will be in the light of the political decisions.'    

In fact, Pakistani forces were battling militants on Sunday in South Waziristan near the Afghan border, an al Qaeda and Taliban stronghold, with military officials saying an offensive was likely there after Swat is secured.

Ali said more financial help would be needed to rehabilitate hundreds of thousands of refugees that left the valley after the Taliban took control of Swat valley a few months back.

He said terror attacks in Pakistan are being funded by drugs money from Afghanistan.

'Unless the poppy cultivation and this nexus between the druglords, the warlords and the Taliban is broken there will be no end to this terrorism which is going on. That is why I have insisted the problem lies in Afghanistan.' - Reuters