VIENNA — The United Nations agency monitoring the nuclear pact between Iran and six world powers reported Thursday that it has found no violations of the deal meant to crimp Tehran’s ability to make atomic arms.

But touching on one potentially sensitive area, the International Atomic Energy Agency said in a review issued Thursday that Iran had begun manufacturing rotor tubes for centrifuges, the spinning machines used to enrich uranium. Iran is allowed to make the parts, but only under certain conditions.

For the 5,060 low-tech centrifuges now producing limited amounts of fuel-grade enriched uranium in Iran, Tehran must use spare parts stripped from old or idle machines. Parts for more advanced centrifuges would fall under even tighter regulations.

Depending on its enrichment level, uranium has a variety of nuclear uses ranging from reactor fuel to the fissile core of warheads.

In its confidential report obtained by The Associated Press, the atomic energy agency said “related technical discussions” with Iran on rotor tube manufacturing are ongoing.

The agency needs to keep a close eye on how many rotor tubes are being made and for what models of centrifuges to make sure they are being produced only in quantities and for machines allowed under the 2015 nuclear agreement that sets a schedule for when and how many advanced centrifuges can be tested.

Any overproduction could hint at possible plans by Iran to expand advanced centrifuge testing beyond pact limits. That could be a significant issue, considering enriched uranium is a potential pathway to nuclear arms because more technically sophisticated models can enrich the uranium much more quickly than Iran’s present mainstay centrifuges.

A senior diplomat familiar with the nuclear deal said details would be shared with the IAEA’s governing board, which includes the United States, Russia, China, France, Britain and Germany — the six powers that struck the deal with Iran last year.

The diplomat said he could not verify reports that the six powers exempted some amounts of low-enriched uranium and facilities from the deal’s scope to allow Iran to be in compliance with the pact from the beginning of implementation in January.

He did say, however, that the IAEA verified that Iran met all the commitments outlined in the deal on implementation day. The diplomat demanded anonymity because he was not allowed to discuss the confidential deal and its implications.