"Iran must cooperate with the IAEA without further delay to fully implement its legally binding safeguards obligations," State Department spokesman Matthew Miller said in a statement, Anadolu reported.

The statement came after the International Atomic Energy Agency (IAEA) claimed in a report on Thursday that Iran is further expanding its nuclear capacities, one week after the agency's board of governors passed a resolution criticizing Tehran's lack of cooperation.

The report showed that Iran aims to continue expanding its nuclear program "in ways that have no credible peaceful purpose," Miller alleged.

"We remain in close coordination with our partners and allies and are prepared to continue to increase pressure on Iran should its non-cooperation with the IAEA continue," he added.

The agency's board of governors passed a resolution a week ago, criticizing Tehran's lack of cooperation with the UN nuclear watchdog despite Tehran's warning not to do so.

Tehran has insisted that the UN watchdog is influenced by the Western states and issues its resoltions under their pressure.

The motion brought by Britain, France and Germany -- but opposed by China and Russia -- at the IAEA's 35-nation board last week was the first of its kind since November 2022.

Iran has called on the IAEA to act technically and not go under the Western states pressures. It has said that the expansion of its nuclear activites is in accordance with the 2015 nuclear agreement known as the JCPOA and its for peaceful purposes. The illegal US withdrawal from the JCPOA in May 2018 forced Iran to take steps back from the deal in retaliation for the Western states violations of the deal.