The United States has admitted for the first time that it delayed in making a 400 million dollar payment to Iran as leverage to ensure that three American prisoners were released.
"The payment of the $400 million was not done until after the prisoners were released," US State Department spokesman John Kirby said on Thursday.
"We took advantage of that to make sure we had the maximum leverage possible to get our people out and get them out safely,” he added.
Kirby noted that it would have been irresponsible for the administration to have acted otherwise.
The admission came after a number of US politicians accused President Barack Obama of paying "ransom" even though the money was owed to Iran.
The Obama administration had earlier denied any connection between the payment and the prisoners. Washington said the payment was part of a decades-old dispute over a failed military equipment deal with Tehran dating to the 1970s, before Iran’s Islamic revolution in 1979.
Both Iranian and US government officials have previously stressed that the payment was unrelated to the nuclear deal struck with the Islamic Republic in July.
The sum returned to Iran, however, constitutes a fraction of the tens of billions of dollars of Iranian assets which the US has blocked since the Islamic Revolution.
In April, the US Supreme Court ruled that Iran's $2 billion of assets held in an American bank be turned over to families of those killed in a 1983 bombing in Beirut and other attacks which Tehran says it has nothing to do with.
Foreign Minister Mohammad Javad Zarif denounced the seizure as “highway robbery” and pledged that Iran would retrieve the sum anyway.