text:  Since Russia's full-scale invasion in 2022, the U.S. and other NATO countries have stepped in, contributing billions of dollars in military aid. A senior U.S. official told NPR that the U.S. is set to give more air defense systems to Ukraine at this week's summit and provide a longer-term commitment to military needs. But Nayim points out that U.S. officials also say Ukraine should not join NATO until it wins the war.