Fighting nears Tripoli, where Quaddafi keeps grip on power

by Kareem Fahim and David D. Kirkpatrick

BAIDA, Libya — As rebellion crept closer to the capital and defections of military officers multiplied, Col. Muammar el-Qaddafi called on thousands of mercenaries and irregular security forces on Wednesday to defend his bastion in Tripoli, in what residents said was a desperate and dangerous turn in the week-old uprising.