By DENNIS CONRAD Associated Press WriterWASHINGTON (AP) _ Democratic presidential hopeful Barack Obama said Thursday he would not use nuclear weapons ‘’in any circumstance.’’ ’’I think it would be a profound mistake for us to use nuclear weapons in any circumstance,’’ Obama said, with a pause, ‘’involving civilians.’’ Then he quickly added, ‘’Let me scratch that. There’s been no discussion of nuclear weapons. That’s not on the table.’’ The Illinois senator warned Pakistani President Gen. Pervez Musharraf earlier this week that he would use U.S. military force in Pakistan even with Musharraf’s permission if necessary to root out terrorists. However, when asked by The Associated Press after a Capitol Hill breakfast with constituents whether there was any circumstance where he would be prepared or willing to use nuclear weapons to defeat terrorism and al-Qaida leader Osama bin Laden, Obama replied: ’’There’s been no discussion of using nuclear weapons and that’s not a hypothetical that I’m going to discuss.’’