NATO allies must address a shortage of critical assets such as aerial refueling aircraft and surveillance drones despite tighter defense budgets on both sides of the Atlantic, US Defense Secretary Leon Panetta said Wednesday. Panetta, in his first speech in Europe since becoming Pentagon chief, prodded the North Atlantic treaty allies to hold defense spending at current levels and said at a minimum they should coordinate any cuts to “avoid surprises” that could endanger each other. “We cannot afford for countries to make decisions about force reductions in a vacuum, leaving neighbors and allies in the dark,” he said in an address to Carnegie Europe, the Brussels branch of the Carnegie Endowment for International Peace think tank. Panetta's remarks echoed those of former Defense Secretary Robert Gates in his last speech in Brussels before leaving office, when he bluntly warned NATO had become a two-tiered alliance divided between those who bear the burden and those who reap the benefits without sharing the costs. But Panetta took a softer approach, balancing concern about the shortage of equipment and personnel.