Rubio demands answers on Iran's nuclear weapon activity amid ongoing bloodshed in Israel

FIRST ON FOX: Sen. Marco Rubio, R-Fla., the vice chairman of the Senate Intelligence Committee, sent a letter to the U.S. State Department on Wednesday calling for a tougher crackdown on Iran and its role in helping carry out the Hamas terrorist attacks on Israel over the weekend.

Rubio, along with several co-signers, including Sens. Bill Cassidy, R-La., Joni Ernst, R-Iowa, Marsha Blackburn, R-Tenn., among others, also want the administration to release information about the International Atomic Energy Agency’s (IAEA) investigation into Iran. The GOP senators criticized the lack of progress in resolving key questions about Iran's nuclear program during a September IAEA Board of Governors meeting.

Over the last five years, the IAEA has been conducting an inquiry into Iran's undisclosed nuclear material and endeavors linked to a covert initiative in 2003 aimed at creating atomic weaponry, known as the Amad Plan. 

"The Iranian regime is intent on fomenting terror across the region, as evidenced by its proxies, Hamas and Hezbollah’s, brutal attacks this weekend on our ally, Israel," Rubio wrote. "Now more than ever, you must ensure that you hold the regime accountable for its failure to comply with obligations under the Nuclear Non-Proliferation Treaty." 

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The Nuclear-Non-Proliferation Treaty, which came into law in 1970, is an international treaty aimed at preventing the spread of nuclear weapons and weapons technology to nonnuclear weapon regions. 

Rubio wrote that despite the IAEA’s repeated attempts to access several Iranian regions, it "has not been able to determine whether Tehran retains covert nuclear weapons activities."

"The Biden Administration has failed to press for concrete action against Iran in Vienna. We are especially disturbed by reports that the United States led efforts to oppose a censure of Iran," Rubio wrote. "As Iran violates its commitments and refuses to comply with the IAEA, your business-as-usual approach to resolving the situation is tantamount to an endorsement of the Iranian regime’s activities."

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He added, "Further, your failure to pursue a censure of Iran, likely in conjunction with ongoing nuclear negotiations with Iran that you continue to conceal from Congress, is simply unconscionable."

According to a congressional report in July, which cited U.S. intelligence assessments, Tehran — the capital of Iran — has the "capacity to produce nuclear weapons at some point," but froze the program and "has not mastered all of the necessary technologies for building such weapons." While both the IAEA and the U.S. government continue to investigate Iran and have not found evidence they are involved in creating any nuclear weapons, they "assess that Iran is more likely to use covert, rather than declared, facilities to produce the requisite fissile material."

However, Rubio said "many questions remain with regard to Iran’s nuclear activities" given several instances where they violated the Safeguards Agreement — the framework for the IAEA to verify that nuclear materials and facilities are used for peaceful purposes and not diverted for any military or explosive purposes — at two sites with undisclosed nuclear activity. 

Rubio joins a growing choir of GOP lawmakers who are seeking answers from the Biden administration on the $6 billion deal with Iran in exchange for five American prisoners last month. 

The deal allowed the transfer of Iran's frozen assets held in a South Korean bank to accounts in Qatar. The administration said the money can only be used for humanitarian purposes, and the U.S. will have oversight as to how and when the funds are used, but it quickly drew skepticism about whether those funds could have been used to fund the surprise attack in Israel. 

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A Hamas spokesperson Ghazi Hamad told the BBC this week that they had Iran’s support for the attacks, which began Saturday. A bombshell Wall Street Journal report Sunday also said Hamas and Hezbollah helped Iran plan the attack — which killed at least 1,200 Israelis and injured thousands more — contradicting the administration's statements.

Treasury Secretary Janet Yellen, speaking Wednesday at the annual International Monetary Fund and World Bank meetings in Marrakesh, Morocco, said the money has not been spent and could be re-frozen.

Fox News Digital has reached out to the State Department for comment on Rubio's letter.

Fox News' Greg Wehner contributed to this report.