Iran and a group of six nations led by the United States have agreed to a historic accord to significantly limit Tehrans nuclear ability for more than a decade in return for lifting international oil and financial sanctions against Iran, a senior Western diplomat involved in the negotiations said on Tuesday.

Some restrictions limiting Irans program begin to phase out after 10 years. Then, after 15 years, Iran would be free to produce as much enriched uranium as it wanted. In theory, though, the Nuclear Nonproliferation Treaty, to which Tehran is a signatory, would prevent it from taking the last steps to produce a weapon.

But the Western diplomat, who spoke on the condition of anonymity because he was discussing confidential talks, signaled that all of the main outstanding issues had been resolved, including the thorny question of how many years an embargo on conventional arms shipments into and out of Iran would remain in place.

The agreement and its annexes run more than 80 pages, Iranian officials said, outlining in painstaking detail how much nuclear fuel Iran can keep in the country for the next 15 years; what kind of research and development it can perform on centrifuges and other nuclear equipment; and the redesign of both a nuclear reactor and a deep-underground enrichment site that Israeli and American officials feared could be invulnerable to bombing.