In a letter to Congress, Secretary of State Rex Tillerson said that Iran is meeting the terms of the 2015 deal worked out with the Obama administration and five other countries. But Tillerson added that the current administration would evaluate whether the lifting of sanctions that had been placed on Iran "is vital to the national security interests of the United States."

"Iran remains a leading state sponsor of terror through many platforms and methods," Tillerson said in his letter Tuesday.

He gave no indication of how long the review would take or what the likely outcome would be. The State Department must provide an update to Congress every 90 days.

Trump was a harsh critic of the deal as a candidate, and his administration has taken a tough line with Iran over a number of non-nuclear issues.