Both he and the Iranian envoy demanded anonymity because they were not allowed to discuss the confidential talks and neither offered details.
Senior Iranian analyst Trita Parsi, citing conversations with Iranian and U.S. officials, said the draft includes a reference to the nuclear Non-Proliferation Treaty, which Iran claims is the guarantor of each country's right to enrich by granting signatories the right to pursue nuclear power for peaceful uses.
That argument is rejected by the United States and its allies, which say the treaty does not directly mention such a right.
Parsi said Tehran wants the wording to make clear that Iran is not a "permanent outcast," but has the same rights and responsibilities as all other signatories to the treaty.
Russia and China in recent years have signaled acceptance of Iran's demand that its right to enrich for peaceful purposes be recognized, and Germany supports the right of any country to that activity as long as it is peaceful. But the other three nations at the table with Iran — the United States, Britain and France — have continued to balk.
The last round of talks between Iran and the six world powers ended Nov. 10 with no deal, even after Kerry, Lavrov, the foreign ministers of Britain, France and Germany and a Chinese deputy foreign minister flew in and attempted to bridge differences.
The United States and its negotiating partners have signaled they are ready to ease some sanctions in return for a first-step deal that starts to put limits on Iran's nuclear program.
They want Iran to stop enriching to a level higher than its main stockpile and only a technical step away from weapons-grade uranium as part of such a deal. They also seek limits on overall enrichment, and a formulation that reduces the proliferation danger from a reactor Iran is building that will produce enough plutonium for up to two weapons once completed.