PARIS (Reuters) -Iran’s acceleration in its enrichment of uranium to close to bomb grade is “extremely serious”, has no civilian justification and contradicts Tehran’s assertions on wanting serious nuclear negotiations, a Western diplomatic source said on Saturday.

Iran has long denied seeking nuclear weapons.

Its foreign ministry said on Saturday that Tehran’s nuclear programme is under continuous supervision of the UN nuclear watchdog International Atomic Energy Agency (IAEA).

The Western diplomatic source, speaking on condition of anonymity, told Reuters the acceleration of enrichment was “in contradiction with Iran’s declarations on its willingness to return to credible negotiations”.

“These measures have no credible civilian justification and could, on the contrary, directly fuel a military nuclear programme if Iran were to take the decision,” the source said.

Rafael Grossi, head of the IAEA, told Reuters on Friday that Iran was accelerating its enrichment of uranium to up to 60% purity, approaching the about 90% level that is weapons grade.

The IAEA later confirmed in a confidential report to member states the accleration in enrichment, a process that refines the raw material so that it can be used as fuel in civil nuclear power generation or, potentially, nuclear weapons.

Responding to Grossi’s remarks and the news of the confidential report, Foreign Ministry spokesperson Esmaeil Baghaei said on Saturday Iran’s nuclear programme is carried out in the framework of the Non-Proliferation Treaty and other safeguards in a “completely transparent manner and under the supervision of the IAEA”.

“The recent activities have also been carried out with detailed information provided to the IAEA and are under its continuous supervision,” Baghaei said, according to Iranian state media.