Sen. Tom Cotton (R-Ark.) blasted the Obama administration Wednesday for reportedly paying Iran the rest of a $1.7 billion in cash, saying the “untraceable” money could serve as a slush fund for terrorists.

“If this report is confirmed, Americans will face the reality that they live in a world where Iran’s terrorist proxies have access to $1.3 billion more in untraceable cash, on top of the $400 million cash payment the administration has already confirmed,” Cotton said in a statement.  

{mosads}”It’s no wonder that the administration has fought so hard to keep the nature and timing of the cash transfers secret,” he said. 

The Obama administration reportedly followed up a January payment of $400 million in cash to Iran after the release of four Americans with two more shipments in the next 19 days, totaling $1.3 billion, according to The Wall Street Journal. 

The Treasury Department confirmed to the Journal that the shipments were made in cash, in the form of Swiss francs, euros and other currencies. 

The money was to resolve a dispute over an arms deal dating to before the Iranian Revolution in 1979, but the timing of the payments — coming only after Iran released four American prisoners — has prompted criticism that they amounted to a hostage ransom. 

Paying ransoms would violate longstanding U.S. policy. The White House has insisted the payments were not ransoms and were in the form of cash since financial sanctions against Iran have made it impossible to transfer the money otherwise. 

The two additional payments occurred on Jan. 22 and Feb. 5 “through Europe,” Obama administration officials reportedly told lawmakers on Tuesday. 

Republicans are vowing to look into the issue now that they’ve returned from recess. Sen. Marco Rubio (R-Fla.) introduced legislation on Tuesday to bar such payments to Iran in the future and reclaim the $1.7 billion the U.S. has paid, to go to victims of Iranian-backed terrorism. 

Lawmakers are concerned that Iran would fund the Lebanese militia Hezbollah, the Bashar al-Assad regime in Syria, Houthi militias in Yemen, or other allies in the Middle East against U.S. interests. 

“The payment of cash ransoms to the world’s worst state sponsor of terror encourages the hostage-taking of more innocent Americans and fuels Iran’s terror plots,” said Cotton. 

“It’s long past time for the president to stop stonewalling on these ransom payments and start being straight with the American people about the dangerous concessions he’s made to the ayatollahs,” he said.