Syrians who fled President Bashar al-Assad's rule fear he may soon be able to choke off badly needed aid as Damascus acts to establish sway over U.N. assistance into the rebel-held northwest, the last major bastion of the Syrian opposition. A tussle at the U.N. Security Council over the aid operation has played to Assad's advantage, with his ally Russia vetoing an extension of its mandate this week and paving the way for Damascus to approve one itself - but on its terms. Aid workers said the outlook for one of the world's biggest humanitarian operations had been thrown into doubt, with Syria's demands for "full cooperation and coordination" raising fears of big complications ahead for their work. "Ever since we heard about the decision, all the families in the camp have been lost, confused, scared," Abu Ahmad Obeid, a father of seven who has lived in a camp in the northwest since fleeing his home in government-controlled territory in 2018, told Reuters by telephone from the region. "We