Netanyahu has said repeatedly the deal is a dangerous one for the Jewish state.

"Israel has many friends and allies but when they're mistaken it's my obligation to speak out clearly and openly and say so," Netanyahu said. "It's my solemn responsibility to protect and defend the one and only Jewish state."

Netanyahu said Israel is not obligated to the deal and Israeli leaders are emphasizing that all options, including a military one, are on the table.

Now, U.S. Secretary of State John Kerry must convince his former Senate colleagues this is a good deal.

"I believe Congress will recognize that this deal actually has a great deal of benefit in it," Kerry said.

Some remain unconvinced.

"Nothing in this deal requires the destruction of any centrifuges," Sen. Saxby Chambliss, R-Ga., said. "They're going to be able to replace centrifuges that become inoperable. And, I just don't see this movement in the direction of preventing Iran from developing a nuclear weapon at all."

After the agreement has been signed, there's a disagreement over one of its key provisions: the right to enrich uranium.

"No, there is no right to enrich," Kerry insisted. "We do not recognize a right to enrich. It is clear in the NPT, in the Non-Proliferation Treaty, it's very, very clear, that there is no right to enrich."

But Iran's president sees the right to enrich uranium as the keystone to this agreement. He said the world powers have now recognized and legitimized Iran's nuclear rights.

"No matter what interpretations are given, Iran's right to enrichment has been recognized in the text of the agreement," Iranian President Hassan Rouhani declared. "And for that reason, I announce to the Iranian nation that Iran's enrichment activity will continue as before."

The deal signed over the weekend is an interim agreement, but Iranian Foreign Minister Mohammed Javad Zarif said negotiations for the next phase could begin in just a few weeks.