Updated

President Trump on Thursday called for an investigation into allegations that the Obama administration tried to give Iran access to the U.S. financial system by sidestepping sanctions.

"The Obama Administration is now accused of trying to give Iran secret access to the financial system of the United States. This is totally illegal," Trump tweeted.

A draft report by the Senate’s Permanent Subcommittee on Investigations found that, in early 2016, the Obama Treasury Department issued a license to Bank Muscat to authorize the conversion of Iran’s rials to euros through “any United States depository institution.”

According to the subcommittee, Iran had $5.7 billion in assets in the Omani bank, and wanted to convert it via the U.S. financial system as it was the most efficient means, “even though U.S. sanctions prohibited it,” according to the report.

The report says that government officials said in subsequent testimony to Congress, though, that Iran would not be granted access to the financial system.

OBAMA ADMIN ALLEGEDLY GAVE IRAN ACCESS TO US FINANCIAL SYSTEM

The report found that the plan failed only when the two U.S. banks refused to participate, citing the complexity and the unwanted appearance involved in processing an Iranian transaction.

By itself, the Obama Treasury Department's issuing of a license to allow Iran to convert $5.7 billion it held at a bank in Oman was not illegal. If the Omani bank had allowed the exchange without such a license, it would have violated sanctions that bar Iran from transactions that touch the U.S. financial system.

But the Senate report revived criticism of how the Obama administration sought to accommodate Iran in connection with the nuclear deal. Trump suggested Thursday that Special Counsel Robert Mueller should be looking at this instead of the Russia probe.

“Perhaps we could get the 13 Angry Democrats to divert some of their energy to this 'matter' (as Comey would call it),” he said. “Investigate!”

Republicans have pointed to the revelation as proof that the Obama administration was "desperate" for the Iran deal.  

"The Obama administration misled the American people and Congress because they were desperate to get a deal with Iran," said Sen. Rob Portman, R-Ohio, who chairs the panel.

But a former administration official disputed the subcommittee's conclusion, saying the Treasury Department never authorized Iran to access U.S. investments or markets, conduct commercial transactions in U.S. dollars or open correspondent accounts at U.S. banks.

“This specific license cannot be described as ‘granting access to the U.S. financial system,’” the former official said. “This specific license was in fulfillment of JCPOA commitments to give Iran access to pools of its money held overseas. It was aimed solely to allow the movement of Iran’s own funds stranded at an Omani bank into euros at a European bank, where Iran could then make use of them.”

Fox News’ Rich Edson and The Associated Press contributed to this report.