A draft nuclear accord now being negotiated between the United States and Iran would force Iran to cut hardware it could use to make an atomic bomb by about 40 percent for at least a decade, while offering the Iranians immediate relief from sanctions that have crippled their economy, officials told The Associated Press on Thursday.

As an added enticement, elements of a UN arms embargo against Iran could be rolled back.

The very existence of a draft provided perhaps the clearest indication the sides were nearing a written agreement as they raced to meet a March 31 deadline for a framework pact. The deadline for a full agreement is the end of June.

Officials said the tentative deal imposes new limits on the number of centrifuges Iran can operate to enrich uranium, a process that can lead to nuclear weapons-grade material. The sides are zeroing in on a cap of 6,000 centrifuges, officials said, down from the 6,500 they spoke of in recent weeks.