With the deadline for a deal on Iran’s nuclear program set for Monday, U.S. President Barack Obama said work remains to be done in the negotiations between the Islamic Republic and the P5+1 group, which consists of the U.S., the U.K., Russia, France and China, plus Germany.

“The gaps are still significant,” Obama said during an exclusive interview on ABC News’ “This Week” Sunday. “I think that our goal has consistently been to shut off a whole bunch of different avenues whereby Iran might get a nuclear weapon, and at the same time make sure that the structure of sanctions are rolled back step for step as Iran is doing what it’s supposed to do.”

Iran and the P5+1 group are currently negotiating in Vienna over an agreement  to scale back the Islamic Republic’s nuclear program in exchange for the lifting of sanctions imposed by the United Nations. However, it unclear whether such a deal can be reached by the deadline Monday, as noted by BBC News.

Although U.S. Secretary of State John Kerry said last week there wouldn’t be a deadline extension, Iran may be looking for one, a source close to the Iranian delegation told Agence France-Presse.

If and when a deal is reached, Obama will have to convince Congress to support it. But he’s optimistic that can happen. “I’m confident that if we reach a deal that is verifiable and ensures that Iran does not have breakout capacity, that not only can I persuade Congress, but I can persuade the American people that it’s the right thing to do,” Obama said on “This Week.”

In the past, Iran has claimed its nuclear program is designed for peaceful purposes, while Western powers have claimed it also could be used for weaponry.