VIENNA/PARIS (Reuters) - The U.N. atomic watchdog policing Iran’s nuclear deal with major powers plans to issue an imminent rebuke to Tehran for failing to provide access to one or more sites that are of interest to it, several diplomats who follow the agency said on Monday.

An Iranian flag flutters in front of the International Atomic Energy Agency (IAEA) headquarters in Vienna, Austria September 9, 2019. REUTERS/Leonhard Foeger

The International Atomic Energy Agency overseeing the landmark 2015 nuclear agreement, which lifted international sanctions against Tehran in exchange for restrictions on its nuclear activities, issues quarterly updates on Iran’s atomic program to its member states.

The next of those quarterly reports is due on Tuesday but, in a first for the IAEA since the deal was put in place, the agency plans to issue a separate report on the same day, calling Iran out for its lack of cooperation in general and its failure to provide access in particular, diplomats said.

“The general message is: There’s a new sheriff in town,” a diplomat from a country on the IAEA’s 35-nation Board of Governors said, referring to new IAEA chief Rafael Grossi of Argentina, who was elected in October with the support of countries including the United States and Brazil.

Grossi took over following the death in office of long-serving IAEA chief Yukiya Amano of Japan, who pressured Iran to provide swifter access to sites of interest to the agency, while avoiding confronting the Islamic Republic publicly, diplomats say.

Under Amano, the IAEA at first resisted public pressure from Israeli Prime Minister Benjamin Netanyahu to visit a site he cited in a speech to the United Nations General Assembly in 2018, calling it a “secret atomic warehouse” mentioned in a trove of data seized by Israeli intelligence agents. Tehran has said the site is a carpet-cleaning facility.

But the IAEA inspected the site in February of last year, diplomats say, and gathered environmental samples that showed traces of uranium that Iran has yet to fully explain.

Now the agency is seeking access to one or more sites mentioned in that trove, which Israel refers to as the “atomic archive” of information on Iran’s former nuclear weapons program.

A spokesman for the IAEA declined immediate comment.

U.S intelligence agencies and the IAEA both believe Iran had a secret nuclear weapons program that it halted long before the 2015 nuclear deal. That deal is aimed at keeping Tehran at least a year away from obtaining enough fissile material for an atom bomb if it sought one.

Iran denies ever having had a nuclear weapons program and says it would never seek to obtain an atom bomb.

It has, however, breached the deal’s restrictions on its atomic activities one after the other in response to Washington’s withdrawal from the deal in May 2018 and its reimposition of sanctions that have choked off the Islamic Republic’s vital oil exports.

“The second report will be on Safeguards issues linked to sites that the IAEA did not get access to. We know of two cases, but we don’t know whether the IAEA will put both in (the report),” said a European diplomat, adding it was unclear what recommendations the agency would make.

Other diplomats said there would be at least one site mentioned in the report, possibly two, and that there was a connection to the archive.

None of the six diplomats who said they expected a second report provided details of the site or sites the reports would likely mention.

NO SUDDEN MOVES

Iran’s breaches of the deal’s nuclear limits on items including the purity to which it enriches uranium and its stock of enriched uranium are eroding the accord, but it says they can quickly be reversed if U.S. sanctions are lifted.

The Trump administration says its “maximum pressure” campaign will force Iran to negotiate a more sweeping deal than the strictly nuclear agreement.

Washington wants a broader deal, covering issues such as Iran’s ballistic missile program and its role in Middle Eastern conflicts like those in Syria and Yemen. It also wants to ban Iran from enriching uranium altogether. Tehran says it will not negotiate unless U.S. sanctions are lifted.

Tuesday’s main IAEA quarterly report is likely to show a jump in Iran’s stock of enriched uranium as Tehran continues to breach key limits of the steadily eroding nuclear deal, diplomats say.

But while Iran breached the deal’s atomic restrictions in the second half of last year, it has refrained from making any large, sudden moves this year, even after the U.S. assassination of its powerful military leader Qassem Soleimani in January, diplomats say.

The level to which it is enriching uranium, for example, remains roughly the same as in the last quarterly report, diplomats say - 4.5% or less, above the deal’s 3.67% limit but still far below the 20% Tehran achieved before the deal and the roughly 90% that is weapons-grade.