President Obama didn’t require Iranian leaders to sign the nuclear deal that his team negotiated with the regime, and the deal is not “legally binding,” his administration acknowledged in a letter to Representative Mike Pompeo (R., Kan.) obtained by National Review.

 “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.

Iranian President Hassan Rouhani discouraged his nation’s parliament from voting on the nuclear deal in order to avoid placing legal burdens on the regime. “If the Joint Comprehensive Plan of Action is sent to [and passed by] parliament, it will create an obligation for the government. It will mean the president, who has not signed it so far, will have to sign it,” Rouhani said in August. “Why should we place an unnecessary legal restriction on the Iranian people?”

Pompeo cited that comment in his letter to Kerry, but Frifield did not explicitly address it in her reply. “This is not a mere formality,” Pompeo wrote in his September 19 letter. “Those signatures represent the commitment of the signatory and the country on whose behalf he or she is signing. A signature also serves to make clear precisely who the parties to the agreement are and the authority under which that nation entered into the agreement. In short, just as with any legal instrument, signing matters.”