Washington: Iran and world powers have reached a historic deal under which Tehran will curb its nuclear program in exchange for the easing of economic sanctions, NBC News confirmed early Tuesday.

Tehran has been negotiating with the U.S., Britain, France, Germany, Russia and China for years, with diplomats extending a series of deadlines in hopes of arriving at a workable plan.

The deal overcame stiff opposition from close U.S. allies like Israel and Saudi Arabia, who say Iran cannot be trusted with a nuclear program of any kind.

After marathon overnight negotiations in Vienna, diplomats clinched the comprehensive agreement — the text of which runs more than 80 pages.

It 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.

While more details were due to be announced at a press conference later Tuesday, the head of the International Atomic Energy Agency confirmed Iran also has signed a roadmap with his organization to clarify outstanding issues.

"This is a significant step forward," Yukiya Amano told reporters.

While he did not provide further details, NBC News confirmed that the deal involves offering sanctions relief to Tehran only once Iran has achieved agreed upon limitations on its nuclear program.

On Tuesday, the European Union said the final plenary between Iran and the six other countries negotiating — known as the P5+1 — would be held at 10:30 a.m. Vienna time (5:30 a.m. EDT), followed by a press conference.

Israeli officials quickly condemned the deal. Prime Minister Benjamin Netanyahy said it gave Iran a "sure path to nuclear weapons," Deputy Foreign Minister Tzipi Hotovely called it a "capitulation of historic proportions," while Science Minister Danny Danon said the deal was "not just bad for Israel, it's dangerous for the entire free world."

Next, the agreement 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.

Iran's moderate President Hassan Rouhani has staked a large share of his political future on a successful outcome of talks. He stands to be one of the biggest winners out of the agreement.

Courtesy NBC News