VIENNA >> Iran has further increased its stockpile of uranium enriched to near weapons-grade levels, a confidential report by the U.N. nuclear watchdog said Saturday. In a separate report, the agency called on Tehran to urgently change course and comply with its years-long probe.

The report comes at a sensitive time, as the administration of U.S. President Donald Trump seeks to reach a deal with Tehran to limit its nuclear program. The two sides have held several rounds of talks, so far without agreement.

The report by the Vienna-based International Atomic Energy Agency — which was seen by The Associated Press — says that as of May 17, Iran has amassed 408.6 kilograms (900.8 pounds) of uranium enriched up to 60%.

That’s an increase of 133.8 kilograms (294.9 pounds) — or almost 50% — since the IAEA’s last report in February. The 60% enriched material is a short, technical step away from weapons-grade levels of 90%. A report in February put this stockpile level at 274.8 kilograms (605.8 pounds).

The IAEA report raised a stern warning, saying that Iran is now “the only non-nuclear-weapon state to produce such material” — something the agency said was of “serious concern.”

Approximately 42 kilograms of 60% enriched uranium is theoretically enough to produce one atomic bomb, if enriched further to 90%, according to the watchdog.

The IAEA report, a quarterly, also estimated that as of May 17, Iran’s overall stockpile of enriched uranium — which includes uranium enriched to lower levels — stood at 9,247.6 kilograms (20,387.4 pounds). That’s an increase of 953.2 kilograms (2,101.4 pounds) since February’s report.

Iran has maintained its nuclear program is for peaceful purposes only, but the IAEA chief, Rafael Mariano Grossi, has warned that Tehran has enough uranium enriched to near-weapons-grade levels to make “several” nuclear bombs if it chose to do so.

Iranian officials have increasingly suggested that Tehran could pursue an atomic bomb.

U.S. intelligence agencies assess that Iran has yet to begin a weapons program, but has “undertaken activities that better position it to produce a nuclear device, if it chooses to do so.”

Iran’s Foreign Ministry and the Atomic Energy Organization of Iran said in a joint statement that the IAEA report was based on “unreliable and differing information sources” and accused it of being biased, unprofessional and lacking crucial, updated information.

“The Islamic Republic of Iran expresses its disappointment about the report, which was prepared by imposing pressure on the agency for political purposes, and expresses its obvious objection about its content,” the statement read.