Republican Sen. Tommy Tuberville's monthslong standoff that has blocked military promotions over the Pentagon's abortion care policy is "putting our national security at risk," three of the nation's senior-most military officials are warning in a Washington Post op-ed that published Monday night.

The op-ed, authored by Navy Secretary Carlos Del Toro, Army Secretary Christine Wormuth and Air Force Secretary Frank Kendall, is an unusual public intervention in a congressional political dispute and reflects the frustration felt at the highest levels of the US military over Tuberville's holds, which have been in place for six months.

"Senators have many legislative and oversight tools to show their opposition to a specific policy. They are free to introduce legislation, gather support for that legislation and pass it. But placing a blanket hold on all general and flag officer nominees, who as apolitical officials have traditionally been exempt from the hold process, is unfair to these military leaders and their families. And it is putting our national security at risk," the leaders write.

Tuberville, of Alabama, has delayed the confirmations of more than 300 top military nominees over his opposition to the Pentagon's policy of reimbursing service members and their families who have to travel to receive abortion care. In the Senate, one senator can hold up nominations or legislation, and Tuberville's stance has left three military services to operate without a Senate-confirmed leader for the first time in history.

It's possible to confirm each of the nominees one by one, but Senate Democrats have argued that would take up valuable floor time -- despite a five-week recess taken in August. The Senate is reconvening on Tuesday.

Without the replacements, the "foundation of America's enduring military advantage is being actively eroded" by Tuberville, and the holds also have "a domino effect upending the lives of our more junior officers, too," the leaders write.

"We know officers who have incurred significant unforeseen expenses and are facing genuine financial stress because they have had to relocate their families or unexpectedly maintain two residences," they write. "Military spouses who have worked to build careers of their own are unable to look for jobs because they don't know when or if they will move. Children haven't known where they will go to school, which is particularly hard given how frequently military children change schools already."

The op-ed concludes, "We believe that the vast majority of senators and of Americans across the political spectrum recognize the stakes of this moment and the dangers of politicizing our military leaders. It is time to lift this dangerous hold and confirm our senior military leaders."

CNN has reached out to Tuberville's office for comment. In July, Tuberville posted on X, "I didn't start this. The Biden admin injected politics in the military and imposed an unlawful abortion policy on American taxpayers. I am trying to get politics out of the military."

Tuberville says the Pentagon is violating law with the reproductive health policies that include, among other things, a travel allowance for troops and their families who must travel to receive an abortion because of the state laws where they are stationed. Pentagon officials have pointed to a Justice Department memo that says the policies are lawful.

The holds first began in March and Tuberville has held his ground despite mounting public pressure.

Active-duty military spouses hand-delivered a petition to Senate Majority Leader Chuck Schumer, Minority Leader Mitch McConnell and Tuberville in July signed by hundreds of military family members who were "deeply concerned and personally impacted by Senator Tuberville blocking confirmation of senior military leaders."

By the end of this year, there will be more than 600 military officers up for nomination, including the nominee for Chairman of the Joint Chiefs of Staff, Air Force Gen. C.Q. Brown, who has been nominated by President Joe Biden to take over for Army Gen. Mark Milley.

Among other positions, the chief of naval operations, Army chief of staff and Marine Corps commandant are serving in acting capacities. In some cases, the officer filling the role on a temporary basis is lower-ranking than the officer who was nominated to take the position; the Missile Defense Agency, for example, is being led by a one-star in an acting capacity despite the position typically being filled by a three-star general.