(CNSNews.com) – “This stuff keeps coming out – drip, drip, drip, drip, drip,” a reporter said during Tuesday’s State Department briefing, as spokesman Mark Toner declined to share details about how $1.3 billion in U.S. taxpayers’ money was paid to Iran last January.

“We’ve been very clear about drawing the line at what we’re going to say about the actual financial transaction,” Toner said. “And bearing in mind that it touches on certain confidentiality, third parties and other parties who might have been involved in that transaction, except to say that we have paid the settlement in full.”

The settlement referred to is the payment of $400 million in Iranian funds which had been frozen for 37 years, plus a negotiated $1.3 billion in interest.

The administration announced the payout in January, but early this month the issue returned to the headlines when the Wall Street Journal reported that the government had secretly airlifted to Iran $400 million, in foreign denomination banknotes packed on wooden pallets in an unmarked cargo plane.

The administration continues to deny that the money amounted to a “ransom” for imprisoned Americans, released by the Iranian regime at the same time as the $400 million was flown into Tehran, on January 16-17.

Last week it did, however, finally acknowledge that the departure of the Americans and arrival of the money were linked, confirming that the handover of the $400 million was contingent on the release of four prisoners.

This week attention turned to the rest of the payout – the $1.3 billion in interest. Investigative reporter Claudia Rosett reported on Monday that on January 19 this year, the Treasury Department sent to the State Department 13 sums of $99,999,999.99 each, plus one of $10 million, adding up to just over $1.3 billion.

The data comes from the Treasury Department’s “Judgment Fund,” which is described as “a permanent, indefinite appropriation available to pay judicially and administratively ordered monetary awards against the United States.”

Toner was pressed on whether the amounts that appear in the Judgment Fund database were the money destined for Iran, and how the transfer was made.

The administration has not confirmed that those sums were indeed the money paid to Iran, but Rosett noted that the Judgment Fund database includes no other payouts over the past year involving the State Department that approach the $1.3 billion sum which the administration says was agreed upon as part of the settlement with Iran.

The database does not indicate what the State Department did with the money – in other words, exactly how it was delivered to the Iranians.

Administration officials have, however, pointed out repeatedly that the U.S. and Iran did not have a financial or bank-to-bank relationship; in Toner’s words on Tuesday, “it was not necessarily an easy or straightforward transaction to make.”

A reporter expressed frustration with the administration’s evident reluctance to open up.

“This stuff keeps coming out – drip, drip, drip, drip, drip,” said the Associated Press’ Matt Lee. “If the administration wants to put it behind itself, it would seem to me that it would be smart to actually get an answer to these questions.”

“I’m aware of your and others’ concerns about this,” Toner said. “I can only say that there are reasons for us withholding this information – I’m talking about the details of this information – to protect the confidentiality [of the transaction].”

Toner tried to defend himself, saying he was not trying to “hide the ball.”

“I’m not accusing – it’s not you that’s the issue here,” Lee said. “It is this hell-bent desire to keep this stuff secret when it’s not secret.”