The Obama administration secretly airlifted $400 million in cash to Iran to settle a decades-old legal dispute as the Iranians in January were releasing four Americans detained by Tehran.
U.S. and European officials and congressional staff briefed on the operation said wooden pallets stacked with euros, Swiss francs and other currency were flown into Iran on an unmarked cargo plane.
The money was the first installment of a $1.7 billion settlement the administration had reached with Iran to resolve a 37-year-old dispute over a failed arms deal signed with Iran just before the fall of Shah Mohammad Reza Pahlavi in 1979.
The legal wrangling was being arbitrated before the international tribunal in The Hague.
Senior U.S. officials denied that the payment was a quid pro quo for the release of the prisoners.
They say the timing was coincidental.