The nuclear agreement, negotiated during Barack Obama's presidency, placed limitations on Iran's nuclear programme in exchange for lifting economic sanctions against Iran.
In a statement that was published, Tillerson stated that Iran continues to stand behind its commitments made in the nuclear deal that was signed in 2015 but the U.S. government is still concerned about how Iran "remains a leading state sponsor of terror".
Secretary of State Rex Tillerson on Tuesday verified to House Speaker Paul Ryan (R-Wis.) that Iran has been complying with the 2015 nuclear agreement.
The nuclear deal was struck in July 2015 after 18 months of negotiations between the U.S., U.K., China, France and Russia, Germany, and Iran.
The secretary of state said the Trump administration was reviewing the lifting of sanctions against Iran, arguing that the country remains a sponsor of terrorism.
"A comprehensive Iran policy requires we address all of the threats posed by Iran and it is clear there are many", Tillerson told reporters at the state department.
The Trump administration certified that Iran is in compliance with the deal it signed with the world powers to rein in its nuclear program.
The US State Department must update Congress on Iran's compliance with the nuclear deal every 90 days.
Defense Secretary James Mattis said last month that Iran continues to export terrorism and sponsor the activity of its ally Hezbollah, a Lebanon-based terrorist group. It is the first such notification under the Trump administration. Congress has already passed bills extending sanctions against Iran, while the US Treasury has announced further sanctions against those closely linked to Iran's Islamic Revolutionary Guard Corps (IRGC) and its clandestine network of global operatives.
This letter certifies that the conditions of Section 135 (d)(6) of the Atomic Energy Act of 1954 (AEA), as amended, including as amended by the Iran Nuclear Agreement Review Act of 2015 (Public Law 114-17), enacted May 22, 2015, are met as of April 18, 2017. Since the sanctions have been lifted, oil exports from Iran to India have surged. If not, Trump will place the U.S.in violation of its commitments and be responsible for unilaterally killing the nuclear deal.