The race is on: Will U.S. aid arrive in time for Ukraine's fight to hold off Russia's army?

The aid is coming at a “vital moment” for the U.S. ally, which faces severe ammunition and personnel shortages that have left it in a desperate situation on the front lines over the last few months, said Neil Melvin, the director of international security studies at the Royal United Services Institute, or RUSI, a London-based think tank. “Russia is gradually grinding down Ukrainian men and weapons,” Melvin told NBC News. “The U.S. supplies can slow this process and potentially blunt an expected Russian counter-offensive over the summer, but Ukraine will need much more if it is to defeat Russia and reclaim its occupied territories.”