The shipment was supposed to consist of thousands of 2,000- and 500-pound bombs, with U.S. concern being how the larger explosives could be used in Rafah.
Authorities said the Guardsman turned around at a Border Patrol checkpoint and fled, leading to a 15-mile chase at speeds of more than 100 miles per hour.
Congress has passed an $825 billion FY24 defense spending bill, but the plan to get Ukraine military assistance across the finish line remains uncertain.
The latest aid comes as the U.S. military remains deeply overdrawn and needs at least $10 billion to replenish all the weapons it has pulled for Ukraine.