BRUSSELS (Reuters) - NATO has signed a 1.1 billion euro contract for 155mm artillery ammunition, the alliance said on Tuesday, 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.

       The contract will likely buy some 220,000 rounds of artillery ammunition, with the first deliveries expected at the end of 2025, a NATO official told Reuters.

       The ammunition will be supplied by French arms maker Nexter and Germany's Junghans, according to an industry source.

       (Reporting by Sabine Siebold and Benoit Van Overstraeten; Editing by Alex Richardson)