AFP/ Washington

US President Barack Obama said on Saturday that diplomacy was the best option to deal with Iran's contested nuclear program, two days after the conclusion of a framework agreement with Tehran.

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.

Echoing comments he made hours after the announcement of the agreement, Obama highlighted the rigorous inspections to which Tehran will be subject.

"If Iran cheats, the world will know it. If we see something suspicious, we will inspect it," he said.

"So this deal is not based on trust, it's based on unprecedented verification."

According to outline text agreed to between Tehran and the P5+1 group -- the United States, Britain, China, France and Russia plus Germany -- Iran must significantly reduce its number of centrifuges in exchange for a suspension of sanctions.

The outline was a major breakthrough in a 12-year international crisis over Iran's nuclear program, but the final deal has yet to be reached.

Iran's arch-foe Israel, widely assumed to have nuclear weapons of its won, reacted strongly against the deal, with Prime Minister Benjamin Netanyahu saying if the text becomes finalized it would "threaten the very survival of the state of Israel."