Bayamon, Puerto Rico ? Barack Obama told veterans Saturday that he can’t understand why Republican John McCain opposes legislation that would provide college scholarships to people who have served in the U.S. military.

Obama’s criticism renews a clash that turned personal after the Senate approved the scholarship bill Thursday.

During the Senate debate, the Illinois senator questioned why McCain, a Navy veteran and former prisoner of war, would oppose the measure. McCain criticized Obama for not serving in the military.

McCain opposes the scholarship measure, as does the Pentagon, because it applies to people who serve just three years. He fears that would encourage people to leave the military after only one enlistment even as the U.S. fights two wars and is trying to increase the size of the Army and Marine Corps.

Instead, McCain proposed a bill to increase benefits in conjunction with a veteran’s length of service. Senate Democrats blocked that measure.