A senior Soviet diplomat said Wednesday that unless the fighting stops in Afghanistan, the estimated 50,000 Red Army soldiers who remain there could stay beyond the Feb. 15 withdrawal deadline. "If a cease-fire holds and there is no fighting in Afghanistan, then that's a very good situation for Soviet forces to leave," Deputy Foreign Minister Yuli Vorontsov told reporters as he arrived in Islamabad. Afghan insurgents headquartered in Pakistan have refused to accept a cease-fire until the current Moscow-backed government in Kabul steps down. Asked whether Soviet troops could overstay the deadline, Vorontsov said, "We shall see. I don't know."