NATO has signed a 1.1 billion-euro ($1.2 billion) contract for 155 mm artillery ammunition, the alliance said, with part of the shells to be supplied to Ukraine after complaints a shortage of munitions was hampering its war efforts. "The war in Ukraine has become a battle of ammunition," NATO Secretary-General Jens Stoltenberg said after a signing ceremony at the alliance's headquarters in Brussels. NATO struck the deal on behalf of several allies who will either pass on the shells to Ukraine or use them to stock up their own depleted inventories. Bulk buying ensures lower prices.