"We write to call attention to a range of obligations that your administration is statutorily mandated to fulfill in relation to Congressional oversight over any such agreement," the letter reads. "We also write to emphasize that we are committed to using the full range of options and leverage available to United States Senators to ensure that you meet those obligations, and that the implementation of any agreement will be severely if not terminally hampered if you do not."
In the letter, Republican senators remind Biden that under the Iran Nuclear Agreement Review Act (INARA), his administration is required to submit any Iran deal to Congress or be blocked otherwise. The lawmakers warned that Iran has made progress toward a nuclear arsenal that will require measures beyond the JCPOA to reverse.
On Monday, State Department spokesman Ned Price was forced to defend a Joe Biden administration waiver that allowed foreign companies to take part in civilian nuclear and safety programmes inside Iran without being subject to sanctions.
US State Department spokesperson Ned Price argues with AP reporter Matt Lee at a presser on February 3, 2022
The Biden administration restored civil nuclear waivers for international nuclear cooperation with Iran on Friday. The State Department has maintained that the sanctions relief was "not a concession to Iran". According to Washington, that would ensure that Tehran was scaling back on its nuclear programme with the hopes it would return to the 2015 deal.
The news of the letter broke as talks to revive the agreement resumed on Tuesday in Vienna. The resumption of the negotiations comes after parties to the original deal cited progress in seeking to restore the 2015 accord in recent weeks.
"A deal that addresses all sides' core concerns is in sight, but if it is not reached in the coming weeks, Iran's ongoing nuclear advances will make it impossible for us to return to the JCPOA", a US State Department spokesperson said on Monday.
Iran, for its part, said that the parties had made "significant progress in various areas of the Vienna negotiations", including on guarantees sought by Tehran that the United States would not violate the pact again.
Answers that "the United States brings... to Vienna will determine when we can reach an agreement", Iranian Foreign Ministry spokesman Saeed Khatibzadeh said on Monday.
Under former President Donald Trump, Washington unilaterally withdrew from the deal in 2018 and reinstated devastating economic sanctions on the Islamic Republic, prompting Tehran to begin scaling back nuclear commitments.
In 2015, Iran signed the JCPOA with the P5+1 group (China, France, Russia, the United Kingdom, and the United States; plus Germany) and the EU. The accord stipulated that Iran curb its nuclear programme in exchange for sanctions relief, including lifting the arms embargo five years after the deal's adoption.