U.S. President Donald Trump has directed the National Security Council to review the international agreement on Iran’s nuclear program and evaluate whether suspending sanctions “is vital to the national security interests of the United States.”

Secretary of State Rex Tillerson revealed the review in a letter Tuesday to House Speaker Paul Ryan.

Tillerson said that as of Tuesday, Iran is complying with its responsibilities under the Joint Comprehensive Plan of Action, which it agreed to in 2015 after negotiations with the U.S., Britain, France, China, Russia and Germany.

“Notwithstanding, Iran remains a leading state sponsor of terror through many platforms and methods,” Tillerson wrote.