Citing unnamed officials briefed on the situation, the newspaper reported that the money was sent to Tehran in stacks of foreign currency aboard an unmarked cargo plane.
Officials claimed the cash had nothing to do with the prisoners' release but was instead tied to a $1.7 billion settlement that the administration had reached with Iran in a dispute over a failed arms deal that dated back to the 1970s.
"With the nuclear deal done, prisoners released, the time was right to resolve this dispute as well," Obama said in January.
While speaking with The Wall Street Journal, senior U.S. officials denied again that the payment was ransom for the American prisoners.
"As we've made clear, the negotiations over the settlement of an outstanding claim … were completely separate from the discussions about returning our American citizens home," State Department spokesman John Kirby told the newspaper. "Not only were the two negotiations separate, they were conducted by different teams on each side, including, in the case of The Hague claims, by technical experts involved in these negotiations for many years."
Secretary of State John Kerry in January hailed the prisoner release as a diplomatic breakthrough. However, Republican lawmakers called for an investigation into the administration's decision to settle, The Washington Post reported, because of worries the cash would appear to be a ransom payment.
In a statement released to Politico Wednesday, Sen. Mark Kirk, R-Illinois, again highlighted those concerns.
"We were right in January 2016 to describe the administration's $1.7 billion transfer to Iran as a ransom payment," he said. "Paying ransom to kidnappers puts Americans even more at risk. While Americans were relieved by Iran's overdue release of illegally imprisoned American hostages, the White House's policy of appeasement has led Iran to illegally seize more American hostages, including Siamak Namazi, his father Baquer Namazi and Reza Shahini."
Republican presidential nominee Donald Trump seized on the claims Wednesday to attack Democratic rival Hillary Clinton, writing in a tweet that, "Our incompetent secretary of state, Hillary Clinton, was the one who started talks to give ($400 million), in cash, to Iran. Scandal!"
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