The State Department refused to say whether it sent Iran $1.3 billion in January, claiming that they were obligated to withhold information about the financial transaction due to confidentiality.

"I've seen the document … I have not had the chance to double check it or check … its accuracy, that it's a legitimate document," spokesman Mark Toner said Tuesday, referring to a Treasury Department website that listed 13 payments of $99,999,999.99, sent to the State Department in January. "There are reasons for us withholding this information, I'm talking about the details of this information, to protect the confidentiality, and that's all I can say right now."

The payments potentially represent the remaining $1.3 billion portion of a $1.7 billion settlement between Iran and the U.S for a failed 1979 arms deal. The first installment, $400 million in cash, was sent to Iran in January around the time that the Islamic Republic released four American hostages, leading to criticism that the payment was for ransom.

The State Department has since admitted that the $400 million, delivered to Iran in an unmarked cargo plane, was used as "leverage," but has maintained that the payment was not quid pro quo.

The administration has said that that payment was sent in cash due to the "strained" state of U.S.-Iranian relations.

"We don't have a banking relationship with Iran," President Obama said this month. "We couldn't send them a check and we couldn't wire the money."

Officials have refused to comment on the remaining $1.3 billion, which the administration claims is interest that has accrued since the failed arms deal, other than to say that it has already been paid.

The 13 payments of $99,999,999.99 were made days after the delivery of $400 million, according to records. Though it is unknown how the $1.3 billion was paid and whether the 13 payments do in fact represent that payment, the finding has raised questions about whether a cash payment was the administration's only option for the $400 million, delivered January 17.

Toner could not explain the potential discrepancy between the $400 million cash payment and the near $1.3 billion payment, which may have been paid by wire. He also refused to confirm that the 13 listed payments represented the $1.3 billion.

"I can see if we can confirm it," he said.