(JNS) Iran has increased its stockpile of highly enriched uranium, the International Atomic Energy Agency (IAEA) said on Thursday.

The UN agency also chastised Tehran for continuing to bar its officials from accessing or monitoring Iranian nuclear sites.

As of Oct. 22, Iran has around 62.3 kg. (137.3 lb.) of uranium enriched to 60% purity, according to the IAEA’s latest quarterly report. This represents a 6.7 kg. increase since the IAEA’s last report in September.

Enrichment to 60% purity is one short step away from 90% weapons-grade fissile material.

Due to restrictions Tehran placed on UN inspectors last year and the regime’s removal of the agency’s monitoring and surveillance equipment from sites in Iran in June, the IAEA said it could not determine the precise size of Iran’s stockpile of enriched uranium.

IAEA Director General Rafael Grossi is “seriously concerned” that Iran has not cooperated with the agency’s investigation into uranium found at three undeclared sites, according to another report.

Separately, the IDF announced on Thursday that two F-35i Adir aircraft accompanied two American B-52 bombers assigned to CENTCOM through Israel’s skies.

The IDF said that the flight was part of the growing cooperation with the US military, which is an important component of Israel’s national security, maintains regional stability and counters regional threats.