More than 20 Republican governors are calling on Congress to remove and prohibit the Biden administration's COVID-19 vaccine mandate for members of the U.S. armed services. 

Tennessee Gov. Bill Lee led 20 other GOP governors in sending a joint letter to congressional leadership Wednesday demanding that Congress revoke the military vaccine mandate either in the upcoming must-pass defense spending bill or through standalone legislation. The Republicans called the mandate "unnecessary" and raised concerns about service members resigning while the military is failing to meet its recruitment goals. 

"The Biden vaccine mandate on our military creates a national security risk that severely impacts our defense capabilities abroad and our state readiness at home," the governors wrote. 

They warned that implementing the mandate "has placed our nation's military readiness at risk." 

TENNESSEE SEN. MARSHA BLACKBURN RENEWS CALL TO PROTECT TROOPS FROM BEING FIRED OVER COVID-19 VACCINE MANDATE

Tennessee Gov. Bill Lee arrives for an event in Washington, D.C., on Thursday, April 30, 2020.  (Jim Lo Scalzo/EPA/Bloomberg via Getty Images)

About 8,000 active-duty service members have been discharged from the Army, Navy, Air Force and Marine Corps since Defense Secretary Lloyd Austin imposed the COVID-19 vaccine mandate in August 2021. Very few applications for religious exemptions have been accepted, with the Army only approving 55 requests from active duty soldiers, one for a National Guard soldier, and one for an Army Reserve soldier, according to Tennessee Sen. Marsha Blackburn's office. 

In October, the Army reported a 25% recruitment shortfall, missing its target by about 15,000 soldiers. Republican lawmakers have cried out against the vaccine mandate, asserting it is contributing to depressed military recruitment. However, the Army has noted that only 23% of 17- to 24-year-olds in America are eligible for service due to failing test scores, obesity rates, concerns over sexual harassment in the military and bountiful employment opportunities as civilians.

In their letter, the governors observed that the National Guard as of September was preparing to discharge approximately 14,000 soldiers over the next two years for refusing to take the COVID-19 vaccines. 

REPUBLICANS DEMAND NAVAL ACADEMY TRANSPARENCY AFTER UNVAXXED MIDSHIPMEN ALLEGEDLY DENIED DIPLOMAS

Military member receives COVID-19 vaccine

A United States Marine receives the Moderna coronavirus vaccine at Camp Foster on April 28, 2021, in Ginowan, Japan. (Carl Court/Getty Images)

"As Governors, our ability to respond to natural disasters and conduct emergency operations is contingent upon the strength and size of our National Guard units," they wrote. "As Congressional leaders, it is your duty to provide for the national defense, and therefore, we call upon you to protect the men and women in uniform—who protect us—from an unnecessary vaccine mandate. As President Biden, himself, stated on September 18, 2022, 'The pandemic is over.'" 

The letter comes just as 13 Republican senators sent their own letter to Minority Leader Sen. Mitch McConnell, R-Ky., and other GOP leadership members demanding that Republicans refuse to advance the National Defense Authorization Act without a vote on military vaccine mandates.

BIDEN DECLARED THE PANDEMIC OVER, BUT UNVAXXED AIR FORCE PILOTS ARE STILL GROUNDED

Defense Secretary Lloyd Austin talks about the Pentagon's national defense strategy

Defense Secretary Lloyd Austin (AP Photo/Susan Walsh)

The effort is being led by Sens. Rand Paul, R-Ky., and Rick Scott, R-Fla., who unsuccessfully challenged McConnell for leadership of the Senate GOP conference. 

"The Department of Defense COVID-19 vaccine mandate has ruined the livelihoods of men and women who have honorably served our country," the Senate GOP letter said. "While the Department of Defense certainly must make decisions that will bolster military readiness, the effects of the mandate are antithetical to readiness of our force, and the policy must be revoked."

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Fox News' Tyler Olson and Kelly Laco contributed to this report.

Read the letter: