Twenty-six Republican senators on Friday condemned the Biden administration’s decision to release $6 billion in frozen Iranian assets in exchange for the release of U.S. hostages held by the regime.

“While we firmly believe the United States must use every appropriate resource to secure the release of American citizens wrongfully detained overseas, this decision will reinforce an incredibly dangerous precedent and will enable the Iranian regime to increase its destabilizing activities across the Middle East,” a letter addressed to Secretary of State Tony Blinken and Treasury Secretary Janet Yellen reads.

The senators added that they are “also worried that your administration is attempting to sidestep Congress and pursue other pathways to financially compensate Iran in an attempt to renegotiate a successor to the ill-fated 2015 nuclear deal.”

The letter argues that the hostage deal violates long-standing U.S. policy and will further encourage further hostage-taking.

The lawmakers requested a briefing on the situation within 30 days and written answers to questions, including whether the administration will offer a specific sanctions waiver for the released funds and what safeguards are in place to ensure the released funds are only used for humanitarian purposes and do not “free up additional resources” for malign activities.

They also asked what “funding mechanisms” have been part of talks around Iran’s nuclear weapons development.