"So far as we know right now, the nuclear technology is considered secure, but there isn't any guarantee, especially given the political turmoil going on inside Pakistan," Clinton said during a Democratic debate.
If elected President, the US senator said, "I would try to get (Pakistan President Pervez) Musharraf to share the security responsibility of the nuclear weapons with a delegation from the United States and, perhaps, Great Britain, so that there is some fail-safe."
The four Democratic candidates - Clinton, Senator Barack Obama, Governor Bill Richardson and former senator John Edwards - were scathing about President George W Bush's policy towards Pakistan.
They said they were prepared to launch unilateral military strikes in the country if they detected an imminent threat or could pinpoint the location of Al-Qaeda chief Osama Bin Laden.
"Here's an unstable leader, Musharraf, in a country with a serious radical - violently radical element that could, under some circumstances, take over the government," warned Edwards.
"If they did, they would have control of a nuclear weapon. They could either use it, or they could turn it over to a terrorist organization to be used against America or some of our allies," he added.