The call was an attempt to help explain the way a $400 million cash payment -- part of a settlement in another dispute -- was handled as leverage for the prisoners. The payment has been criticized as ransom for the prisoners, a charge the administration sought to debunk Friday.
"There was truly a profound lack of trust on this very difficult prisoner exchange track," a senior administration official said of the secret talks with Iran, "and even over the final 48 hours, there were repeated indications that our people may not actually ever be permitted to leave Iran."
In those crucial hours, the official said, the Iranians leaked information about the deal to the media, detained the American prisoners at the airport as they were preparing to leave and even led negotiators to believe they might return the prisoners to Tehran's notorious Evin prison.
Also of concern, the official said, was the disappearance in the final hours of Yeganeh Salehi, an Iranian citizen who is married to released Washington Post reporter Jason Rezaian and was included in the exchange.
According to the official, her whereabouts were even unknown to delegation of Iranian negotiators in Geneva, Switzerland, leading some to speculate there might have been internal attempts within Iran to sabotage the deal.
"So a number of things were going on which caused us great concern," the official said.
Around the same time, issues were popping up in the US.
Iranian prisoners -- some of them dual citizens -- who were being released from US jails in exchange for the Americans were refusing to return to Iran, raising suspicions on the Iranian side, the official said.
"One of the Iranian-Americans in a US prison then refused his pardon initially," said the official, "and the Iranians in Geneva said that, unless he accepted his pardon, they would not release our people. ... The Iranians thought we were pulling a fast one on them, because why would this guy not accept his pardon?"
It was under these circumstances, the official said, that the US decided to hold up a $400 million payment to Iran, which they owed as part of settlement in a Hague tribunal case and had planned to make on the same day as the exchange to take advantage of the momentum of the moment.
"It would have been irresponsible under these circumstances for us to move ahead with the separate Hague settlement and subsequent payment unless and until we knew the Americans were free," the official said. "What we thought and hoped would be a smooth culmination day ended up being hardly that."
When a video emerged earlier this month that purportedly showed the payment of $400 million on the same day the prisoners were released, the Obama administration was hit with accusations they'd paid a ransom for the Americans.
At the time, officials denied there was any connection between the payment and the exchange. But when The Wall Street Journal reported this week that the money had been held until the prisoners were let go, the narrative began to change.
On Thursday, the State Department's spokesman, John Kirby, said the US used the $400 million as "leverage" to address concerns Iran might renege on the release.
Nevertheless, officials insist the payment was not a "random" or a "quid pro quo" as some critics have deemed it.