Pakistan's US-allied president must resign before next month's elections or the country could risk slipping into civil war, opposition leaders and an independent research group said Thursday. The calls came after the government decided to postpone crucial parliamentary polls until February 18, six weeks after they were initially scheduled, due to unrest following the assassination of opposition leader Benazir Bhutto. The opposition urged Musharraf, the former army chief who seized power in a 1999 coup, to resign. "Free and fair polls are impossible under his leadership," said Javed Hashmi, a senior member of former Prime Minister Nawaz Sharif's party. "Such a thing is unthinkable if he is there."