BRUSSELS: America's military alliance with Europe - the cornerstone of US security policy for six decades — faces a “dim, if not dismal” future, US Defense Secretary Robert Gates said Friday in a blunt valedictory address to the Security and Defense Agenda thinktank here. In his final policy speech as Pentagon chief, Gates questioned the viability of NATO, saying its members' penny-pinching and lack of political will could hasten the end of US support. The North Atlantic Treaty Organization was formed in 1949 as a US-led bulwark against Soviet aggression, but in the post-Cold War era it has struggled to find a purpose. “Future US political leaders — those for whom the Cold War was not the formative experience that it was for me - may not consider the return on America's investment in NATO worth the cost,” he told a European think tank on the final day of an 11-day overseas journey. Gates said both of NATO's main military operations now — Afghanistan and Libya — point up weaknesses and failures within the alliance. “The blunt reality is that there will be dwindling appetite and patience in the US Congress - and in the American body politic writ large - to expend increasingly precious funds on behalf of nations that are apparently unwilling to devote the necessary resources or make the necessary changes to be serious and capable partners in their own defense,” he said. He blasted allies who are “willing and eager for American taxpayers to assume the growing security burden left by reductions in European defense budgets.” Gates said America's partners were running short of munitions after 11 weeks of air raids in Libya. “Frankly, many of those allies sitting on the sidelines do so not because they do not want to participate, but simply because they cannot,” he said. He said the NATO-led ground war in Afghanistan had scored important accomplishments but said the mission, along with the Libya war, had reflected chronic underinvestment and at times a lack of political backbone. In Afghanistan, Gates said it was worrying that an alliance with two million in uniform has “struggled, at times desperately, to sustain a deployment of 25,000 to 45,000 troops” and faced shortages of helicopters, transport aircraft, maintenance and surveillance planes. Gates acknowledged that the Libyan mission has met its initial military goals of grounding Muammar Gaddafi's air force and limiting the regime's ability to launch attacks against civilians. However, he said many allies lacked intelligence and surveillance aircraft and specialists, which meant the US military had to step in to ensure that allied fighter jets could identify and strike targets.