NATO defense ministers Friday tackled the controversial issue of how to pay for Afghanistan's expanding security forces after they assume responsibility for the war in 2014. Since Afghanistan — one of the world's poorest nations — cannot foot the estimated $6 billion (€4.6 billion) annual bill, NATO nations will have to pay the bulk of it. But austerity measures and budgetary cuts caused by the financial crisis in the United States and Europe are making it difficult to raise the money. British Defense Secretary Philip Hammond said ministers would consider two critical questions: “What should be the long term size of the Afghan security forces and how are we going to share the cost of supporting that between different members of the international community. Those are discussions we have started here and we will continue at Chicago,” he said The two-day meeting in Brussels of ministers from NATO's 28 nations and 22 other countries taking part in the war in Afghanistan is meant to pave the way for a NATO summit in May in Chicago. The Afghan army and police are scheduled to grow to more than 350,000 members by 2014. But some have proposed that the force can be safely cut to about 250,000 in order to save on costs. The Taliban insurgents are estimated to have about 20,000 men under arms. A related unresolved question that will also be take up in Chicago is the number of US and other foreign troops that might remain behind and what missions they would be assigned. The debate on costs came after NATO allies agreed broadly on Thursday to step back from the lead combat role in Afghanistan and let local forces take their place as early as next year, a shortened timetable that startled officials and members of the US Congress.