United Nations — The U.S. and other global powers are grappling with how to respond to the recent discovery of uranium particles in Iran that were enriched up to almost 84% — very close to the purity required to make nuclear weapons. A team of inspectors from the United Nations' International Atomic Energy Agency (IAEA) found the tiny amount of high enriched uranium at one of Iran's nuclear facilities during a scheduled visit and included it in their report.

The IAEA report, obtained by CBS News, noted the discovery of some particles enriched to 83.7% at the Fordow nuclear plant, but did not conclude that Iran was stockpiling uranium enriched above 60%, which the world already knew Iran was doing. Any uranium refined to over 60% purity is considered high enriched, and at any such level it is a relatively short technological step to achieve the 90% required for weapons.

Iran has long said it does not intend to build nuclear weapons and insisted that its atomic work is entirely for civilian medical and research purposes. The country explained the latest findings of the IAEA team as the result of "unintended fluctuations."

Iran has methodically ramped up its enrichment program for several years — without hiding the moves — as a response to the U.S. government, under former President Donald Trump in 2018, unilaterally withdrawing from the Iran nuclear deal (known by the acronym JCPOA) that imposed limits on its atomic work.

Negotiations to strike a new deal or revise the one the U.S. walked away from have foundered, and various signatories to the pact, which include Iran, Russia, China, France, Germany, the U.K. and U.S., have been alarmed by every one of the steps forward by Iran in the interim. The discovery of even trace amounts of uranium enriched so close to 90% set alarm bells ringing yet again this week.

"We are highly concerned by the IAEA Director's General confirmation of the presence of high enriched uranium (HEU) particles containing up to 83.7% U-235 at the Fordow facility," Peter Stano, lead spokesman for Foreign Affairs and Security Policy of the European Commission, told CBS News.

Stano said discussions between the IAEA and Iran to clarify the matter were ongoing and expected to conclude "soon," but he didn't speculate on their outcome.

Some JCPOA signatories including the U.S. argue there is no legitimate need in a civilian nuclear program for uranium enriched to even 60%, which they note is well above the limit that had been imposed by the agreement. The pact limited Iran's uranium stockpile to 661 pounds and its enrichment level to 3.67%, which is what's needed for the country's nuclear power plants.

Next step: Censuring Iran?

A report in The Wall Street Journal cited diplomats involved in the discussions as saying the U.S. and its European nations were split on how to respond to the findings in the latest IAEA report. A high-ranking U.S. official familiar with the talks told CBS News, however, that there was "no split," but the U.S. was concerned by the revelation.

Israel, a staunch foe of Iran, has said it will not allow the Islamic republic to achieve weapons-grade enrichment of uranium, laying it down as a "red line."

"At this point, the question is whether there should be a censure resolution against Iran at the IAEA's Board of Governors next week," Ali Vaez, of the International Crisis Group thinktank, told CBS News, referring to the mechanism within the agency by through which its global members can lodge a formal complaint.

IAEA Director-General Rafael Grossi arrived Friday in Iran, and Veaz said if he manages to resolve at least some of the concerns during his one-day visit, "especially the 84% enrichment issue, then it [a formal censure of Iran] can be avoided."

Vaez said the only "disagreement" among the Western powers was that the "U.S. prefers to wait for the outcome of the trip before it decides about censuring Iran, whereas the Europeans seem keen on doing it anyway."

The IAEA said in its report that it would "increase the frequency and intensity of agency verification activities" at Fordow given the discovery of the high enriched uranium particles.

The European Union has been pushing hard to wrap up the ongoing talks about reviving the 2015 nuclear deal with Iran.

Spano, of the European Commission, which is the EU's executive branch, said the new concerns about Iran's enrichment activities "only underlines how important it is to conclude the talks about reviving the JCPOA as soon as possible, since this deal provides an international oversight of Iran's nuclear program and would bring Iran back to respecting and fulfilling its commitments."

Pamela Falk

Pamela Falk is the CBS News correspondent covering the United Nations, and an international lawyer.

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