Mattis argued the agreement, which involves the U.S. and five other countries lifting its sanctions on Iran in exchange for restrictions on its nuclear program, is integral to security in the region. “When America gives her word, we have to live up to it and work with our allies,” Mattis said.
Source Article from http://theiranproject.com/blog/2017/01/13/james-mattis-in-major-break-with-trump-insists-u-s-must-live-up-to-iran-deal/