U.S. Secretary of State Rex Tillerson says Iran is sticking to the terms of the historic agreement it made to curb its nuclear program.
But he also says the Trump administration is questioning whether the U.S. should continue holding up its side of the bargain.
Under the 2015 Joint Comprehensive Plan of Action, the U.S. and five other powers agreed to lift some sanctions on Iran if the country would restrict its nuclear activities.
But this week, Tillerson argued in a letter to House Speaker Paul Ryan that Iran is still "a leading state sponsor of terror."
And he said President Donald Trump has ordered an interagency review to figure out if continuing to lift sanctions against Iran is "vital" to the national security interests of the U.S.
As CNN notes, if the U.S. were to reapply sanctions against Iran, it would go against the terms of the JCPOA.
Trump has repeatedly expressed his disdain for the agreement.
"I think it was the worst deal I've ever seen negotiated," Trump told Fox News.
But his predecessor Barack Obama insisted the deal was the best way to prevent Iran from building nuclear weapons.
It's unclear exactly how long the Trump administration's review will take.