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President Barack Obama fiercely defended the historic nuclear deal with Iran as he faced White House reporters Wednesday at a press conference.

"The bottom line is this. This nuclear deal meets the national security interest of the United States and our allies," the president said. "It prevents the most serious threat, Iran obtaining a nuclear weapon, which would only make the other problems that Iran may cause even worse. That’s why this deal makes our country and the world safer and more secure."

Six world powers, including the United States, reached the deal on Tuesday. It aims to limit Iran’s nuclear capability in exchange for lifting punishing economic sanctions. Obama has said the deal eliminates every pathway to an Iranian nuclear weapon.

The president is also keenly aware that it will take work to convince U.S. lawmakers, especially those who have expressed deep skepticism, to support the agreement.

"I expect the debate to be robust, as it should be," the president said on Wednesday.

During the press conference, the president referred to notes and dissected point by point the type of criticism leveled at the deal since it was announced. He also said that critics of the deal have not presented a better alternative and indicated that he was ready for an engaged conversation on the matter.

"I suspect this is not the last we’ve heard of this debate," the president said.

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Related: Imperfect Balance: Experts Say Iran Nuclear Deal a Step Forward

The deal still faces a vote in Congress, although it is unclear whether Republicans and some Democrats who object to the deal will actually be able to override the decision — and Obama threatened Tuesday to veto any attempt to reject the accord.

Republicans have said it amounts to appeasement of a dangerous regime. Sen. Lindsey Graham of South Carolina, a presidential candidate, said on TODAY that the deal was like throwing gasoline on a fire.

After House Democrats emerged from a briefing Wednesday morning with Vice President Joe Biden, New York Democrat Rep. Steve Israel said he is a "skeptic" of the agreement, but will take the entire 60-day review period to figure out if this deal is worth supporting.

"I think the vice president made as convincing of an argument as he can make, but I think there are a lot of questions to be answered," Israel said. "I had been skeptical from the beginning of this. I am still skeptical. I read the Joint Comprehensive plan of action last night and there was nothing in it to relieve my skepticism."

Israeli leadership has been more blunt in its criticism.

Prime Minister Benjamin Netanyahu of Israel told Lester Holt that Iran "has two paths to the bomb: One if they keep the deal, the other if they cheat on the deal."

The agreement involves limiting Iran's nuclear production for 10 years and Tehran's access to nuclear fuel and equipment for 15 years in return for hundreds of millions of dollars in sanctions relief.

However, the sanctions would not be lifted until Iran proves to the International Atomic Energy Agency that it has met its obligations under the terms of the deal. The agreement also includes the provision of a "snap back" mechanism that could lead to the reinstatement of sanctions within 65 days if Iran violates the terms of the deal, according to officials.

The head of the International Atomic Energy Agency confirmed Iran also has signed a roadmap with his organization to clarify outstanding issues.

The agreement also makes no mention of the four Americans who have been held in Iran for years, a fact Obama said "nobody is content" over in fiery remarks.

Nuclear and foreign policy experts say that while the agreement isn't perfect it is the best option on the table right now.

"The deal will happen," said David Rothkopf, a former Clinton administration official and editor of Foreign Policy Group, a collection of foreign policy publications. " Congress can't stop it. So its critics ought to start focusing on how to make it work in the context of a broader strategy rather than simply trying to score political points."