The four Democratic candidates - Hillary, 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 Pakistan"s tribal areas bordering Afghanistan if they detected an imminent threat or could pinpoint the location of al-Qaeda chief Osama Bin Laden.
Edward warned Musharraf is an unstable leader, and added that radical element could take over the government.
''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,'' a foreign news agency quoted Edward, as saying.
Obama reiterated his earlier stance that if there is strong intelligence on al-Qaeda in Pakistan he would take action even if Islamabad is opposed to it.
Meanwhile, Richardson called for Musharraf's ouster. "What I would specifically do as president is I would ask Musharraf to step aside," Richardson said.