Iran and six world powers determined the outlines of a landmark agreement which would curb Iran's nuclear program and potentially lift economic sanctions.

As Obama gears up to sell US skeptics on the deal, he said he is convinced talks are the best way forward. "As President and Commander in Chief, I firmly believe that the diplomatic option a comprehensive, long-term deal like this is by far the best option," Obama said in his weekly address.

Explaining that he expects a "robust debate" on the deal in the United States, Obama said he will keep Congress apprised of the "substance of the deal."

Many of Obama's Republican opponents in Congress have been skeptical of a deal with Iran and suggested the US may be giving too much away in its negotiations.

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