GENEVA (AP) - Iran struck a historic nuclear deal Sunday with the United States and five other world powers, in the most significant development between Washington and Tehran in more than three decades of estrangement between the two nations.
The agreement commits Iran to curb its nuclear activities in exchange for limited and gradual sanctions relief. It builds on the momentum of the dialogue opened during September's annual U.N. gathering, which included a 15-minute phone conversation between President Barack Obama and Iran's new president, Hassan Rouhani.
Obama hailed the deal's provisions as key to preventing Iran from proliferating. "Simply put, they cut off Iran's most likely paths to a bomb," he told reporters.
Switzerland's Foreign Minister Didier Burkhalter, left, shakes hands with Iranian Foreign Minister Mohammad-Javad Zarif, during a meeting at the Intercontinental Hotel prior to talks about Iran's nuclear programme in Geneva, Switzerland, Saturday, Nov. 23, 2013. -- (AP Photo / Keystone, Martial Trezzini)
The deal marks a milestone between the two countries, which broke diplomatic ties 34 years ago when Iran's Islamic revolution climaxed in the storming of the U.S. Embassy in Tehran. Since then, relations between the two countries have been frigid to hostile - until the recent outreach between the two presidents.
Obama hailed the deal as putting "substantial limitations" on a nuclear program that the United States and its allies fear could be turned to nuclear weapons use.
"While today's announcement is just a first step, it achieves a great deal," Obama said. "For the first time in nearly a decade, we have halted the progress of the Iranian nuclear program, and key parts of the program will be rolled back."
Although the deal lowered tensions between the two countries, friction points remain - notably Iran's support of the Syrian regime of Bashar Assad. The United States has accused Iran of supporting terrorism throughout the region and of widespread human rights violations.
A White House statement called the nuclear agreement an "initial, six-month step."
Specifically, the statement said the deal limits Iran's existing stockpiles of enriched uranium, which can be turned into the fissile core of nuclear arms.
The statement also said the accord curbs the number and capabilities of the centrifuges used to enrich and limits Iran ability to "produce weapons-grade plutonium" from a reactor in the advanced stages of construction.
The statement also said Iran's nuclear program will be subject to "increased transparency and intrusive monitoring."
"Taken together, these first step measures will help prevent Iran from using the cover of negotiations to continue advancing its nuclear program as we seek to negotiate a long-term, comprehensive solution that addresses all of the international community's concerns," said the statement.
In return, the statement promised "limited, temporary, targeted, and reversible (sanctions) relief" to Iran, noting that "the key oil, banking, and financial sanctions architecture, remains in place." And it said any limited sanctions relief will be revoked and new penalties enacted if Iran fails to meet its commitments.
Those conditions have been highlighted by the Obama administration in its efforts to persuade Congress to hold off on any new sanctions and give the Iran accord a chance to prove its worth. But one influential member of Congress was quick to criticize the deal.
Ed Royce, the Republican chairman of the House Foreign Affairs Committee, expressed "serious concerns," saying the United States was "relieving Iran of the sanctions pressure built up over years," while allowing Tehran to "keep the key elements of its nuclear weapons-making capacity."
Royce called on U.S. Secretary of State John Kerry to "address the many concerns with this agreement" in front of the committee.
Kerry flew to Geneva on Saturday, joining forces with foreign ministers of the nations negotiating with Iran to push the deal through early Sunday, as the negotiations entered their fifth day.
"Agreement in Geneva," Kerry tweeted. "First step makes world safer. More work now."
Kerry said the first-step deal will make Israel - an arch enemy of Iran - safer. He was trying to pacify Israel's vehement opposition to the deal.
Israel Prime Minister Benjamin Netanyahu has loudly criticized the agreement, saying the international community is giving up too much to Iran, which it believes will retain the ability to produce a nuclear weapon and threaten Israel.
Israeli Intelligence Minister Yuval Steinitz, who is responsible for monitoring Iran's nuclear program, said there is no reason for the world to be celebrating. He says the deal, reached in Geneva early Sunday, is based on "Iranian deception and self-delusion."