The Trump administration notified Congress Tuesday that Iran is complying with the landmark nuclear deal negotiated by former President Obama, and has extended sanctions relief given to Tehran in exchange for curbs on its atomic program.

Secretary of State Rex Tillerson, in a letter to House Speaker Paul Ryan, R-Wis, said that the administration has undertaken a full review of the agreement to evaluate whether continued sanctions relief is in the best interest of the U.S.

"Iran remains a leading state sponsor of terror, through many platforms and methods," Tillerson wrote. He said the National Security Council-led interagency review of the agreement will evaluate whether it "is vital to the national security interests of the United States."

Tillerson noted that Iran is still considered a leading state sponsor of terrorism and that President Trump had ordered the review with that in mind.

The certification of Iran's compliance, which must be sent to Congress every 90 days, is the first issued by the Trump administration.

Trump criticized the Iran nuclear deal during his presidential campaign, but had not made it known whether he would scrap it, modify it or keep it in place with tougher enforcement.

The nuclear deal was sealed in Vienna in July 2015 after 18 months of negotiations led by former Secretary of State John Kerry and diplomats from the other four permanent members of the U.N. Security Council — Britain, China, France and Russia — and Germany.

Under its terms, Iran agreed to curb its nuclear program, long suspected of being aimed at developing atomic weapons, in return for billions of dollars in sanctions relief.

Opponents of the deal, including Israel, objected, saying it only delayed Iran's pursuit of nuclear weapons and did not allow for the kind of inspections of its atomic sites that would guarantee it was not cheating.

The Associated Press contributed to this report.