“The Joint Comprehensive Plan of Action (JCPOA) is not a treaty or an executive agreement, and is not a signed document,” wrote Julia Frifield, the State Department assistant secretary for legislative affairs, in the November 19 letter.

Frifield wrote the letter in response to a letter Pompeo sent Secretary of State John Kerry, in which he observed that the deal the president had submitted to Congress was unsigned and wondered if the administration had given lawmakers the final agreement. Frifield’s response emphasizes that Congress did receive the final version of the deal. But by characterizing the JCPOA as a set of “political commitments” rather than a more formal agreement, it is sure to heighten congressional concerns that Iran might violate the deal’s terms.

“The success of the JCPOA will depend not on whether it is legally binding or signed, but rather on the extensive verification measures we have put in place, as well as Iran’s understanding that we have the capacity to re-impose — and ramp up — our sanctions if Iran does not meet its commitments,” Frifield wrote to Pompeo.