U.S. President Donald Trump has said Iran is not living up to the "spirit" of its nuclear deal with world powers, an assessment that followed media reports that he intends to decertify the landmark 2015 accord.
Since the Trump came into power, he desperately wants to remove the nuclear pact and get rid of the limits it imposes on the U.S. ability to exert more hostile policies against Iran.
U.S. President Donald Trump waves after arriving by helicopter at Morristown Airport to depart aboard Air Force One bound for Washington in Morristown, New Jersey, U.S. August 14, 2017.
Opponents say it went too far in easing sanctions without requiring that Iran end its nuclear program permanently.
During the same hearing, General Joseph Dunford said he believed Iran is not in material breach of the accord, which he said has delayed Tehran's nuclear capability.
It is expected that Mr Trump will give a major foreign policy speech on October 12, in which he will accuse Iran of fuelling terrorism and causing instability in the Middle East.
The International Atomic Energy Agency (IAEA) is fresh from verifying Iran's compliance as recently as last month, while other parties to the agreement are also on board, except the United States leader.
Mr Trump has until 15 October to decide.More news: 'Santa Claus' tomb discovered in Turkey
If Trump were to decertify the agreement, the decision would be left to Congress as to whether economic sanctions would be returned to Iran.
The agreement provided Iran with billions of dollars in sanctions relief in exchange for widespread curbs on and access to its nuclear programme.
The president addressed the reporters and said, "You guys know what this represents?"
Trump has accused Iran that it "did not follow the spirit of the agreement" signed during the presidency of Barack Obama.
The White House has not yet clarified what the president intended by his "calm before the storm" remark.
Mattis suggested not leaving the agreement on Iranian nuclear program, since there is now no evidence of violations by Tehran and it meets the interests of Washington.
When reporters attending the event asked what the President's comment meant, Trump replied: "It could be, the calm, the calm before the storm". He was meeting with the military officials to discuss strategy for North Korea and Iran.
In fact, James Mattis has no formal say in the final decision on JCPOA, the US Secretary of Defense revealed how the presidential office might work to increase pressure on Iran while remaining party to the JCPOA.