The White House says that the US has paid $1.3 billion in interest to Iran, as part of a settlement from the Iran-US Claims Tribunal in The Hague. The payment was interest that had accrued over decades on $400 million in Iranian funds frozen by the US in 1981.

"The $1.3 billion payment has been made. It was made through a transaction involving central banks but obviously not the U.S. central bank because there are extensive restrictions on the financial relationship between the United States and Iran," White House Press secretary Josh Earnest said.

The US State Department said last week that 400 million US dollars in cash was released to Iran only after it was assured that four Americans held prisoner in Iran had been released. It's the first time the US administration has publicly said that it used the payment as leverage to ensure the prisoners had been released. President Barack Obama and Secretary of State John Kerry have both denied that the payment was a ransom for the release of the prisoners or tied to the Iran nuclear deal.