Iowa Senator Chuck Grassley is joining the chorus of critics accusing the Biden Administration of releasing six-billion dollars to Iran in order to secure the release of five Americans being held hostage. Grassley and fellow Republican Senator Tim Scott of South Carolina have sent a letter, asking the White House about what they’re calling a “secret deal” with Iran.

A New York Times report says President Biden negotiated the release of the hostages in exchange for unfreezing Iran’s assets in South Korea, transferring the near-six-billion dollars to an account in the central bank of Qatar (kah-TAR). In a tweet on Monday, Grassley said, “That’s a lot of money to fund more terrorism + will make taking Americans hostage more likely.” Grassley talked with Iowa reporters in a conference call on Tuesday morning.

According to the Times, Biden administration officials have declined to comment or to confirm details about the agreement. Grassley is incensed the U-S would negotiate with Iran, which he says is negotiating with terrorists.

Reports say three of the Americans were being held in Iran on unsubstantiated charges of spying. The other two are reportedly a scientist and a businessman.