Alabama Sen. Tommy Tuberville’s standoff with the Biden administration over a Department of Defense policy funding access to abortions for military personnel intensified Thursday when a bipartisan group of seven former U.S. Secretaries of State expressed their opposition in a letter to Senate leaders.

The former Pentagon leaders said in the letter that the hold Tuberville has placed on promotion or reassignment of almost 200 military officers “is harming military readiness and risks damaging U.S. national security.”

Tuberville placed the hold in response to a Defense Department policy to cover travel expenses and paid leave for military personnel who travel for abortion services. The policy would fund those expenses for personnel stationed in states, such as Alabama, where abortion access is restricted. Tuberville has said he objects because Congress did not approve the use of taxpayer money.

Typically, military promotions and reassignments are approved by the Senate in an informal process known as unanimous consent. The hold blocks that practice. Promotions and reassignments can still be approved by the Senate through a floor vote.

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The seven secretaries of defense served in recent presidential administrations. Robert Gates worked for Presidents George W. Bush and Barack Obama. William Perry, William Cohen, Leon Panetta and Chuck Hagel worked for President Bill Clinton. James Mattis and Mark Esper worked for President Donald Trump.

The letter was addressed to Senate Majority Leader Chuck Schumer and Minority Leader Mitch McConnell.

“We appreciate that senators can have sincere and legitimate concerns about a Pentagon policy, including how it may relate to broader domestic or social issues,” the letter said. “These lawmakers also deserve timely and thorough responses to their questions. However, we believe placing a hold on all uniformed nominees risks turning military officers into political pawns, holding them responsible for a policy decision made by their civilian leaders.”

In an Op-Ed published Wednesday on AL.com, Tuberville defended the holds.

“Back in November I heard the Pentagon was thinking about using our tax dollars to facilitate elective abortion,” Tuberville said. “There’s nothing in the law that allows the Pentagon to do that. Congress never took a vote on it. In fact, Congress has voted to strictly limit the instances in which DOD can perform abortion.

“I warned the Secretary of Defense directly in December that if he insisted on flouting the law, I would use my authority as a senator and slow down their highest-level nominations in the Senate. Secretary Austin blatantly ignored me (and more than a dozen other senators) and implemented his illegal plan to fund unrestricted access to abortions.”

In their letter, the secretaries of state cited specific positions affected by the hold that could diminish the military’s ability to maintain checks on Iran and China as well as coordinating support for Ukraine.

“Leaving these and many other senior positions in doubt at a time of enormous geopolitical uncertainty sends the wrong message to our adversaries and could weaken our deterrence,” the letter said.

Tuberville, however, has repeatedly disputed the suggestion that military readiness is jeopardized through his holds.

“During a recent Senate Armed Services Committee hearing, Chairman Jack Reed (D-RI) asked a top combatant commander what impact my hold has on readiness,” Tuberville said in the Op-Ed. “In response, the commander said ‘operationally’ the holds have ‘no impact’ because military leaders remain in their posts until they are replaced.”