US Defense Secretary James Mattis said that the United States should consider staying in the Iran nuclear agreement unless it were proven that Tehran was not abiding by the agreement or that it was not in the US national interest to do so. <br/><br/>Although Mr. Mattis said he supported President Donald Trump's review of the agreement curbing Iran's nuclear program, the defense secretary's view was far more positive than that of US President. <br/><br/>Mr. Trump has called the agreement agreed between Iran and six world powers in 2015 an embarrassment. Mr. Mattis said that Mr. Trump is weighing whether the agreement serves US security interests or not.