Rand Paul wants President Barack Obama to seek congressional approval of any further nuclear deal with Iran.

While Paul is a rare Senate Republican that has declined to antagonize the president legislatively on the issue, the Kentucky lawmaker wrote Obama on Thursday seeking answers on what Congress’s role will be as diplomatic negotiations continue with Iran.

“On a foreign policy issue of this magnitude, it is my strong belief that any further agreement – be it interim or final – that lifts statutory sanctions on Iran should require approval by the Congress before taking effect. Please let me know if it is your intent to seek this approval for any subsequent interim or final deal,” Paul said in the letter, which was also addressed to Secretary of State John Kerry as well as the leadership of the Senate Foreign Relations Committee.

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Paul was following up on questions he posed to one of Obama’s point people on Iran negotiations, Undersecretary of State Wendy Sherman. He sought information about Obama’s authority to relax existing economic restrictions on Iran as a result of the country’s compliance with an interim, six-month deal that winds down some of Iran’s nuclear ambitions in returning for an easing of some sanctions.

“The intent of Congress was not simply to allow the President to waive all the sanctions in perpetuity at his behest,” Paul said in the letter. “Like you, I am hopeful a peaceful resolution can be reached. However, in the course of those negotiations, it is both my hope and expectation that the Congress will continue its role as an integral participant in our foreign policy toward Iran.”

Paul and Jeff Flake of Arizona are the only two Senate Republicans that have not cosponsored a popular Senate bill that would slap new economic penalties on Iran if diplomatic talks fall through or Iran violates the interim deal. Both lawmakers said in recent interviews that they do not have plans to sign onto that legislation unless ongoing negotiations between Iran and global powers are disrupted.

“I think it’s still a good idea to see if Iran is going to comply with negotiations at this point,” Paul said. But, he added: “I haven’t made a final decision. We’re going to wait and see if anything changes.”