FIRST ON FOX: A coalition of 18 House Republicans led by GOP Conference Chair Elise Stefanik, R-N.Y., are pressing Energy Secretary Jennifer Granholm over her agency's invitation for foreign adversaries to inspect a sensitive U.S. nuclear testing site.

In a letter sent Thursday morning, Stefanik and the other Republicans blasted Granholm for recently offering China and Russia "unprecedented access" to the Department of Energy's (DOE) Nevada National Security Site. Bloomberg reported in September that the DOE's National Nuclear Security Administration invited Chinese and Russian officials to tour the site to prove the U.S. is upholding a three-decade moratorium against testing nuclear weapons.

"I am leading my colleagues in demanding that President Biden revoke this misguided invitation to our adversaries in Beijing and Moscow that grants them unprecedented access and insight into our nuclear weapons," Stefanik told Fox News Digital. "Inviting Communist China and Russia to have a front row seat for our sensitive nuclear weapons tests will give them invaluable information on how to defeat our nuclear capabilities and improve their own."

"At a time when our adversaries are growing their nuclear stockpiles to undermine America’s leadership allowing them access to one of our nuclear test sites will only advance this pursuit and lead to our own destruction," she continued.

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The National Nuclear Security Administration invited its Chinese and Russian counterparts to tour the Nevada site — where sensitive nuclear experimentation is conducted — during the latest International Atomic Energy Agency summit, according to Bloomberg. Corey Hinderstein, a senior National Nuclear Security Administration official, said China and Russia didn't immediately respond to the invitation.

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The invitation came months after Russian President Vladimir Putin suspended his nation's participation in the only remaining nuclear arms control pact with America. And last week Putin signed a law withdrawing Russia from its ratification of a global treaty banning nuclear weapons tests in a move quickly condemned by the State Department and which is evidence of deteriorating relations between the two sides.

Rep. Doug Lamborn, R-Colo., who was one of the co-signers of Stefanik's letter to Granholm on Thursday, said allowing foreign adversaries to observe U.S. nuclear testing activities "allows them to derive our methods and procedures and this destroys deterrence."

"As Chairman of the House Armed Services Strategic Forces Subcommittee, one of my priorities has been to strengthen and protect our nuclear arsenal," he told Fox News Digital. "In the world today, nothing could jeopardize our national security more than losing this advantage. I was stunned to hear recent reports of Biden administration officials inviting citizens from our two greatest adversaries to observe U.S. nuclear weapons tests."

"Russia and China should not have insider access to our testing. Both countries have had ample opportunity to be more open about their nuclear weapons development and deployments and refuse to do so. The amendment I introduced on this matter will halt the Biden administration's latest lapse in judgment," the Colorado lawmaker continued.

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Late last month, Lamborn introduced a bill to block foreign nationals from witnessing U.S. nuclear weapons testing at national labs. The bill was attached to the Fiscal Year 2024 Energy and Water Development and Related Agencies Appropriations Act which the House passed on Oct. 26.

The letter Thursday also comes as China continues to expand its own nuclear capabilities and armament. Stefanik, Lamborn and the other GOP lawmakers noted the Department of Defense has warned China’s nuclear expansion is exceeding previous U.S. projections.

"The PRC is now projected to have over 1,000 warheads by the end of this decade," General Anthony Cotton, the commander of the U.S. Strategic Command, told lawmakers during an Armed Services Committee hearing in March.

In their letter, the Republicans told Granholm that China now has no reason to halt the aggressive expansion of its nuclear development "if they are given this access while offering nothing in return." They further noted that China has refused to engage in discussions on its nuclear expansion and DOE's actions threaten to "embolden their efforts to continue growing their arsenal."

"The notion of granting America’s adversaries’ access to our military sites — and enabling them to gain information about U.S. nuclear capabilities — is deeply alarming and fundamentally absurd," Rep. Rob Wittman, R-Va., another letter co-signer, told Fox News Digital. 

"I am proud to join my colleagues in demanding the Biden administration explain why they are inviting Russian and Chinese Communist Party officials to access our most sensitive laboratories and testing facilities." 

In addition to Stefanik, Lamborn and Wittman, fellow GOP Reps. Joe Wilson, James Moylan, Bill Posey, Pat Fallon, Chris Smith, Ashley Hinson, Carlos Gimenez, Scott DesJarlais, John Moolenaar, Lance Gooden, Brett Guthrie, Dale Strong, Julia Letlow, Robert Aderholt and Brad Wenstrup also co-signed the letter.

The DOE didn't immediately respond to a request for comment.