An Israeli soldier is seen in the Israeli-occupied Golan Heights, on May 9, 2018. The decision of U.S. President Donald Trump to quit the 2015 international nuclear deal with Iran pushed Israel to go on high alert over Syria, as Israel has reportedly instructed local authorities in the Israeli-occupied Golan Heights to prepare bomb shelters in case of any Iranian offensive. (Xinhua/JINI/Ayal Margolin)

UNITED NATIONS, July 1 (Xinhua) -- UN Secretary-General Antonio Guterres is concerned by reports that Iran may have exceeded limits on its low-grade enriched uranium stockpile, his spokesperson said Monday.

"The secretary-general is very much aware of the reports that the Islamic Republic of Iran may have surpassed its JCPOA (Joint Comprehensive Plan of Action) limits on its low-enriched uranium stockpile," said Stephane Dujarric, spokesman for Guterres. "He is concerned by such reports."

Dujarric said if verified, such action by Iran "would not help preserve the plan (JCPOA) nor secure the tangible economic benefits for the Iranian people. It's essential that this issue, like other issues related to the implementation of the plan, be addressed through the mechanism established by the JCPOA."

According to the official IRNA news agency, Iranian Foreign Minister Mohammad Javad Zarif said on Monday that Iran's low-grade enriched uranium stockpile has exceeded 300 kg.

Zarif, whose remarks were made in the central Iranian city of Natanz, home to parts of Iran's nuclear facilities, also said the European signatories of the JCPOA, had taken "insufficient" measures to ensure Iran's benefit from the accord after the U.S. exit in May 2018.

The foreign minister later insisted in a tweet that Tehran had not violated the nuclear agreement.