Oren Dorell

USA TODAY

The State Department confirmed Thursday that a $400 million cash shipment to Iran in January was tied to the release of four American citizens who’d been detained in the country.

Spokesman John Kirby said negotiations over the United States’ return of Iranian money from a decades-old frozen account were conducted separately from talks to release the prisoners. But he said the U.S. withheld delivery of the cash as leverage until the U.S. citizens had left Iran.

Both events happened on Jan. 17.

"Payment of the $400 million was not done until the prisoners were released," Kirby said, according to an unofficial transcript. While he refused to provide a "tick-tock" of the release of the money and the prisoners, "they came together near simultaneously," Kirby said. "We retained maximum leverage until the Americans were released."

The admission came after the Wall St. Journal reported that the four Americans were released through a carefully orchestrated deal that included removing sanctions from Iran Air the day before the release of U.S. Pastor Saeed Abedini, Washington Post Tehran Bureau Chief Jason Rezaian, former U.S. Marine Amir Hekmati and a businessman Nosratollah Khosrawi-Roodsari. All four are Iranian-born, dual U.S.-Iranian citizens who were visiting or working in Iran when they were detained.

The shipment, on pallets loaded with Euros, Swiss Franks and other currency, was loaded onto an Iranian cargo plane in Geneva, Switzerland, but not allowed to depart for Iran until a Swiss Air Force craft with the Americans on board was allowed to depart from Tehran, the Journal reported.

President Obama denied on Aug. 4 that the payment was tied to the detainees’ release, saying the money was the first installment of the lifting of sanctions called for by the 2015 nuclear agreement with Iran. It was money the United States owed Iran from a failed arms deal that predated the 1979 Islamic Revolution in Iran that brought the current government into power, the White House said.

“We do not pay ransom for hostages,” Obama said at the time.

Republicans pounced on the news Thursday. At a rally in Charlotte, GOP presidential nominee Donald Trump called the transaction ransom for hostages.

Republican lawmakers leveled the same criticism “Today, the State Department admitted what we’ve long suspected – that the president and his administration have been misleading us since January about whether he ransomed the freedom of the Americans unjustly imprisoned in Iran," House Speaker Paul Ryan, R-Wis., said in a released statement on Twitter. "The president owes the American people a full accounting of his actions and the dangerous precedent he has set.”

Sen. Tom Cotton, R-Ark., said reports about the transaction "confirm what many of us have suspected all along: The $400 million payment to Iran was a ransom payment for four Americans unlawfully held by the ayatollahs. He added that “terrorist groups and our adversaries around the world” know the U.S. will pay “cold, hard cash for hostages,” Cotton said.. Dianne Feinstein, D-Calif., said critics are making political hay of the matter, when in fact American officials showed good judgement.

Democrats defended the transaction. "We're in campaign season. Misconstruing what somebody says, particularly from the (Obama) administration has become an art form," Sen. Dianne Feinstein of California told CNN.

The Iranians wanted money they were owed, but the U.S. only released the money after the detainees were released, she said. "I think they made the right judgement."