U.S. Defense Secretary Leon Panetta said Wednesday his country under budgetary pressure was no longer able to make up shortfalls in capabilities of NATO European members. \"Many might assume that the United States defense budget is so large it can absorb and cover alliance shortcomings, but make no mistake about it, we are facing dramatic cuts with real implications for alliance capability,\" Panetta told the Brussels-based organization Carnegie Europe, adding the Pentagon is facing 450 billion U.S. dollars in reductions over the next 10 years. The Pentagon chief said although the Libya mission demonstrated the importance of NATO, it revealed \"growing gaps\" and \"significant shortfalls in capabilities\" within the military alliance, which the United States had to make up. \"Nowhere were the gaps more obvious than in the critical enabling capabilities: refuelling tankers, provision of intelligence, surveillance, and reconnaissance platforms such as Global Hawk and Predator drones. Without these capabilities, the Libya operation would have had a very difficult time getting off the ground or been sustained,\" he said. \"There are legitimate questions about whether, if present trends continue, NATO will again be able to sustain the kind of operations that we have seen in Libya and Afghanistan without the United States taking on even more of the burden,\" he said before attending his first NATO defense ministers\' meeting on Wednesday and Thursday. He urged the European allies to halt additional cuts in defense and coordinate their movements to ensure limited resources to be put into \"the most efficient and effective defense programs.\" \"We cannot afford for countries to make decisions about force structure and force reductions in a vacuum, leaving neighbors and allies in the dark. This must be a transparent and cooperative process,\" he said.