Iran offered Tuesday to clear up suspicions about its disputed nuclear activities if the Security Council ends its "interference," in an apparent attempt to head off new sanctions for its refusal to freeze uranium enrichment.

The overture, contained in a restricted document made available to The Associated Press, came as the five permanent council members deliberate on a new resolution aiming to tighten up the sanctions against Iran for its nuclear defiance.

The document — a letter to the International Atomic Energy Agency — said Iran was ready to "negotiate ... for the resolution of outstanding issues with the IAEA ... without the interference of the United Nation(s) Security Council."

While Iran has made such offers before, renewing it now seemed to be linked to the moves in New York, even though diplomats involved in working on a new draft resolution cautioned that any agreement was some time off.

Signed by Ali Ashgar Soltanieh, Iran's chief representative to the IAEA, the letter also said Tehran was ready to "enter a constructive ... negotiation" meant to resolve the impasse over its refusal to mothball its enrichment program.

That offer also has been made before by top Iranians. But it has repeatedly been rejected by the five Security Council permanent members and Germany because the Islamic republic refuses their precondition that it first mothball its enrichment activities. Iranian opposition to freezing first and talking later doomed both previous talks and then later attempts to restart them.

Enrichment is a key issue because it can be used to make the fissile core of nuclear warheads, although Tehran insists it wants to enrich only to low levels used to generate power.

Iran has enriched small quantities of uranium to the low level suitable for nuclear fuel generation. The U.S. and its allies fear that Iran could build nuclear weapons with larger amounts of more highly enriched uranium.

Earlier Tuesday, Iranian Foreign Minister Manouchehr Mottaki denied his country has slowed its nuclear program, contradicting remarks by IAEA head Mohamed ElBaradei that Tehran appeared to have paused enrichment. Mottaki said enrichment was continuing unabated.

"Iran's legitimate activities with the aim of producing fuel ... are continuing their natural trend," Mottaki told a news conference. "There has been no change in that course."

Iran's Atomic Energy Organization also said there had been no change in the enrichment schedule. ElBaradei had said Monday that Iran appeared to have at least temporarily paused on the development of its uranium enrichment program.

Elbaradei also said the IAEA cannot be sure if Iran's nuclear activities are peaceful or a cover for a weapons program until Tehran cooperates with his experts.

China urged Iran on Tuesday to fully open its nuclear program to U.N. inspections, as a meeting of the IAEA moved toward slashing technical aid programs for Tehran because of its defiance of the U.N. Security Council.

"We welcome, support and call upon Iran to step up cooperation with the International Atomic Energy Agency," Chinese Foreign Minister Li Zhaoxing told reporters in Beijing, picking up on a theme raised by ElBaradei in Vienna.

Unless Iran takes "the long overdue decision" to cooperate with the IAEA, it "will have no option but to reserve its judgment about Iran's nuclear program," he said.

Iran, which says its nuclear program is intended only to create fuel for power plants, has enriched small quantities of uranium to the low level suitable for nuclear fuel generation. The U.S. and its allies fear that Iran could build nuclear weapons with larger amounts of more highly enriched uranium.

Hard-line President Mahmoud Ahmadinejad had been expected to announce last month that Iran had started installing 3,000 uranium-enriching centrifuges at a facility in the desert outside the central city of Natanz, where it has about 500 centrifuges above and below ground. But the announcement never materialized, an apparent step back that ElBaradei appeared to confirm Monday.

Up for review as early as Tuesday at the Vienna meeting of the IAEA's 35 board nations will be a Feb. 22 report from ElBaradei finding that Iran has set up hundreds of centrifuges as part of its continuing enrichment efforts.

The board was expected to approve last month's decision by ElBaradei to suspend nearly half the technical aid his agency provides to Iran. Only North Korea and Saddam Hussein's Iraq have faced such punishment in the past.

The European Union said it backed the suspensions, saying it "supports the (IAEA) ... views" on the 23 projects that could be suspended — 18 contained in the most recent recommendations and five frozen earlier.

The board also will be reviewing North Korea's apparent willingness to ultimately dismantle its nuclear arms-making capabilities.

The Security Council's permanent members and Germany are currently discussing strengthening sanctions imposed on Iran in December for its refusal to halt enrichment.

Meanwhile, the official Islamic Republic News Agency reported that Iran's military tested anti-aircraft defenses at another nuclear facility, near the central Iranian city of Isfahan. The report did not elaborate and officials at the Isfahan governor's office declined comment.

The report said the tests lasted three hours. Isfahan residents were notified in advance so the tests would not be mistaken for an airstrike against the plant, nine miles outside Isfahan.