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U.S. Sen. Mark Kelly speaks at an event hosted by the Environmental Defense Fund and Valley Metro.

More than 300 military promotions are on hold. Republican Sen. Tommy Tuberville of Alabama has stalled them in hopes of overturning a federal policy that helps military members access medical services, including abortion.

Arizona Sen. Mark Kelly is adding his voice to the many calling for Tuberville to stand down.

“He clearly doesn’t understand how damaging this is to our force,” Kelly said. “Or he doesn’t care.”

Kelly said Tuberville’s actions are damaging national security.

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“This isn’t just about holding up admirals and generals; this has cascading effects through the officer ranks,” Kelly said.

For the first time since the Civil War, the Marine Corps has no Senate-confirmed leader.

The position is one of the Joint Chiefs of Staff, which includes the head for each military branch, a chair and vice chair. The chair will step down Oct. 1. Nominees to head the Army and Navy are also on hold.

“When an individual can’t be promoted, can’t move on to their next position,” Kelly said, “they’re going to get frustrated and they’re gonna leave the military. So, we potentially could lose significant leadership.”

Reportedly, the number of blocked promotions could double by the end of the year.