TEHRAN, Iran (AP) – In a fresh display of brinksmanship, Iran indefinitely postponed talks on a proposed solution to the standoff over its nuclear ambitions Monday and diplomats in Europe said Iranian scientists had resumed small-scale enrichment of uranium.

Depending on the degree of processing, enriched uranium can be used in nuclear reactors or atomic bombs.

Talks scheduled for Thursday about moving Iran’s uranium enrichment to Russia to allay international concerns that it could develop nuclear weapons have been postponed indefinitely because of the “new situation,” Iranian presidential spokesman Gholamhossein Elham said.

Iran uses the “new situation” to describe the International Atomic Energy Agency’s decision this month to report the country to the U.N. Security Council because Iran had not offered convincing proof it was not seeking nuclear weapons.

Diplomats told The Associated Press in Vienna, Austria, Monday that Iran has started small-scale enrichment of uranium, a process that can be used to make fuel for civilian reactors or nuclear weapons, depending on the degree of enrichment.

“Uranium gas has been fed into three machines,” one senior diplomat familiar with Iran’s nuclear file said on condition of anonymity because he was not authorized to speak on the matter.

To produce significant amounts of enriched uranium, gas must be fed into hundreds of centrifuges.

Iran is years away from running the 50,000 centrifuges it says it wants to produce fuel for its Russian-built nuclear plant at Bushehr.

Even small-scale enrichment is significant because it represents symbolic determination to move forward with a technology that most nations want Iran to give up.

Iran maintains that its nuclear program is designed solely to generate electricity, but the United States and some allies claim it is a cover for producing a bomb.

The Security Council is expected to consider steps against Iran that could include sanctions after the IAEA, the U.N. nuclear watchdog, issues a report on the issue next month.

Iran has strongly protested its referral to the Security Council, which was supported by Russia, usually one of Tehran’s allies.

Analysts believe Iran has enough uranium for about five crude nuclear weapons. Estimates on how long Iran needs to enrich it range from three to 10 years.

After the IAEA voted on Feb. 4 to report Iran to the Security Council, Iran ended voluntary cooperation with the agency and announced it would start large-scale enrichment and bar surprise inspections of its facilities. It has yet to announce whether any uranium enrichment, large- or small-scale, has begun.

On Monday, Elham was asked if Iran was delaying the resumption of large-scale enrichment until after an IAEA meeting in March. He replied “no,” but did not elaborate.

Moscow proposed Iran ship its uranium to Russia, where it would be enriched to a level suitable for nuclear reactors. It would then be returned to Iran for use at the Bushehr plant, which is due to begin operating this year.

The plan, backed by the United States and the European Union, was an attempt to avoid international objections to Iranian uranium enrichment, by providing oversight so no weapons would be made. Iran had said the plan did not fulfill its requirements but was worth pursuing.

Elham said the talks would reconvene at a time of “mutual agreement.”

Russia did not mention Elham’s statements in a Monday announcement that its foreign minister would discuss Tehran’s nuclear program with European Union leaders in Vienna this week.

In Berlin, German Foreign Ministry spokesman Jens Ploetner said his government regretted Iran’s decision.

Elham also reiterated President Mahmoud Ahmadinejad’s statement Saturday that Iran will “revise” its policy toward IAEA regulations and the Nuclear Nonproliferation Treaty if they are used against the country _ a veiled threat to withdraw from the pact.

Elham said the world must recognize Iran’s rights as a signatory to the treaty and regulations.

“Otherwise there is no reason to continue our current nuclear policy while we are deprived of the positive aspects of the treaty,” he said.

Tehran has stressed repeatedly that the treaty allows it to pursue a nuclear program for peaceful purposes and says it will never give up the right to enrich uranium for nuclear fuel.

Elham also repeated an Iranian pledge that any sanctions on Iran would backfire.

“If some Western countries, provoked by Israel, intend to put pressure on Iran, then they will also lose. We do advise the United States and Europe to decide in a rational and prudent way,” he said.

Much of the surveillance equipment and seals from Iran’s nascent uranium enrichment facilities has been removed by the Iranians since they announced they would resume limited activities there. Iran also decided to end the agency’s rights to in-depth nuclear inspections at short notice.

The moves left the IAEA with few means to monitor Tehran’s enrichment efforts and look for secret sites and experiments that could be linked to nuclear arms.