The Iranian regime’s retention of key nuclear weapons sites and material for building atomic bombs — highly enriched uranium — has led to new efforts by the U.S. and Israeli to take out the last vestiges of the regime's program.

On Friday, the Israel Defense Forces (IDF) said in a statement that its "Air Force Struck the Arak Heavy Water Plant — A Key Plutonium Production Site for Nuclear Weapons." The Arak plant is located in central Iran.

Prior to Friday's attack, an IDF spokesperson, speaking in reference to Arak, told Fox News Digital there is a "high estimation" that attacks on "uranium enrichment sites are part of the plan.":

The IDF declined to answer more specific questions about its target list and if any ground operations to retrieve the nuclear weapons-grade uranium were being considered.

NEXT MOVE ON IRAN: SEIZE KHARG ISLAND, SECURE URANIUM OR RISK GROUND WAR ESCALATION

Reuters, quoting regime media outlet Fars, reported that joint U.S.-Israeli strikes on Friday hit the Khondab heavy water research reactor. 

A statement released by the IDF said, "Heavy water is a unique material used to operate nuclear reactors, such as the inactive Arak reactor, which was originally designed to have weapons-grade plutonium production capabilities. These materials can also be used as a neutron source for nuclear weapons.

"The plant was a significant economic asset for the terror regime and served as a source of income for the Iranian Atomic Energy Organization, generating tens of millions of dollars for the regime each year."

The regime's foreign minister posted a condemnation of Israel and warned the Jewish state, "Iran will exact HEAVY price for Israeli crimes."

According to an article published by the Washington, D.C.-based Institute for Science and International Security (ISIS), "The IR-40 Arak, aka Khondab, Heavy Water Reactor and Heavy Water Production Plant date to the early 2000s. … The reactor core design was ideal for making substantial amounts of weapon-grade plutonium for nuclear weapons."

STRIKES MAY SET IRAN BACK — BUT LIKELY WON'T END NUCLEAR PROGRAM, UN WATCHDOG CHIEF SAYS

Jason Brodsky, the policy director of United Against Nuclear Iran (UANI), told Fox News Digital, "The one nuclear site which hasn’t been hit to date has been Pickaxe Mountain, so striking that site as part of Operation Epic Fury will be important to further degrade the Iranian nuclear program."

A White House spokesperson referred Fox News Digital to President Trump’s Cabinet meeting comments about Iran’s nuclear weapons program. 

"We're free to roam over their cities and towns and destroy all of their crazy nuclear weapons and missiles and drones that they're building," Trump said Thursday.

David Albright, a physicist, founder and president of the Institute for Science and International Security, told Fox News Digital that with respect to key nuclear weapons facilities that remain, "The elephants in the tent are Natanz and Isfahan. There was an attack on Natanz that the Iranians revealed, but the Israelis said we are not aware of an attack. So, it must have been the U.S."

TRUMP SAYS US, ISRAEL SHATTERED IRANIAN MILITARY CAPABILITIES, PRESSES LEADERS TO SURRENDER: 'CRY UNCLE'

He said Natanz has enriched uranium. 

"The Iranians were doing recovery operations in the underground fuel enrichment plant there and continuing to build this Pickaxe Mountain tunnel complex, which could hold enriched uranium. Right next to it is another tunnel complex that was built much earlier, around 2007. … And the Iranians sealed it up, fortified it. There is something obviously important there."

Albright said U.S. and Israeli airstrikes "have not attacked the underground Isfahan site. We know, according to the IAEA [International Atomic Energy Agency], highly enriched uranium is in that site. There may be an enrichment plant under construction in that underground complex. We would like that site to be attacked."

Albright warned that the war should not end like the previous U.S.-Israel war with Iran in 2025 with Tehran retaining the "crown jewels" of its atomic weapons program — highly enriched uranium and a number of centrifuges.

"You don’t want it to come out of this war with the same kind of nuclear weapons capabilities that it had at the end of June war with a higher incentive to build a bomb," Albright said. That is why it's so important "to finish the job" in Iran, he added.