WASHINGTON, July 2 (Xinhua) -- The Pentagon said Wednesday that U.S. strikes last month on three key Iranian nuclear facilities have set back Tehran's nuclear program by as much as two years.

"We have degraded their program by one to two years, at least intel assessments inside the department assess that," Sean Parnell, a Pentagon spokesperson, said at a news briefing, without providing further details.

"All of the intelligence that we've seen led us to believe that Iran's, those facilities especially, have been completely obliterated," Parnell added.

On June 22, U.S. forces bombed the three Iranian nuclear facilities of Natanz, Fordow, and Isfahan.

"No one exactly knows what has transpired in Fordow," Iranian Foreign Minister Seyed Abbas Araghchi told CBS News in an interview Tuesday. "What we know so far is that the facilities have been seriously and heavily damaged."

Iran's Atomic Energy Organization is assessing the damage, he added.

Iranian President Masoud Pezeshkian issued an order on Wednesday to enact a law suspending the country's cooperation with the International Atomic Energy Agency (IAEA).

The law calls for a suspension of cooperation with the IAEA until Iran's sovereignty, territorial integrity, and the safety of its nuclear facilities and scientists are fully guaranteed, said Constitutional Council Spokesman Hadi Tahan Nazif.

The law requires that any future inspections of Iran's nuclear sites by the IAEA need approval from the Supreme National Security Council.

In response, the IAEA said in a statement, "We are aware of these reports. The IAEA is awaiting further official information from Iran."

Speaking at a daily press briefing on Wednesday, Stephane Dujarric, chief spokesman for UN Secretary-General Antonio Guterres, expressed concern over Iran's decision, calling it "obviously concerning."

"The Secretary-General has been very consistent in his call for Iran to cooperate with the IAEA, and frankly, for all countries to work closely with the IAEA on nuclear issues," he said.

U.S. State Department spokeswoman Tammy Bruce said Wednesday that Iran's suspension of cooperation with the IAEA is "unacceptable."

"We'll use the word unacceptable, that Iran chose to suspend cooperation with the IAEA at a time when it has a window of opportunity to reverse course and choose a path of peace and prosperity," Bruce told a briefing.

Iran must cooperate fully with the UN agency without further delay, she said.