Best option for the Unites States at this point, regarding 'regional and global realities', is to stay in Iran nuclear deal, the head of an American think tank has said, according to IRNA.

'Opting to stay in Iran nuclear deal doesn't mean it isn't flawed. It is. But best U.S. option at this point given regional & global realities,' Richard Hass, president of the Council on Foreign Relations, wrote on his Twitter page on Tuesday, October 3, following the remarks by U.S. Defense Secretary James Mattis in support of Iran nuclear deal.

Earlier in the day, Mattis said that it would not be in the U.S. national security interest if President Donald Trump canceled the Iran nuclear deal.

Iran and the five permanent members of the UN Security Council plus Germany signed the agreement in 2015, upon which Iran accepted to curb its nuclear activities in exchange for sanctions removal.

Trump has frequently threatened that he would scrap the deal. In his speech at the 72nd session of the UN General Assembly in September Trump described the deal as an 'embarrassment' and 'one of the worst and most one-sided transactions the United States has ever entered into.'