The State Department confirmed Monday that the Obama administration has paid Iran another $1.3 billion to settle a failed arms deal from 1979, but couldn't describe who in the Iran government it paid, and couldn't say what form that payment took — cash, check or otherwise.

The State Department also admitted it can't guarantee that the Iran Revolutionary Guard Corps wouldn't be able to get its hands on the money eventually.

"We can always hand it over to someone who can hand it over to the IRGC," State Department spokesman Mark Toner told reporters. Many in the U.S. see the IRGC as being responsible for helping to finance terrorism.

The administration agreed to pay Iran $1.7 billion to compensate that country for its payment to the U.S. in 1979 for military equipment. That deal fell through after Iran's government was overthrown, and the Obama administration has said it owes Iran this money, plus interest.

The first installment of the payment was a $400 million cash payment, which has drawn criticism from Republicans. They say it looks like a ransom payment to ensure the release of American hostages who Iran released this year.

When asked how the remaining $1.3 billion was paid, Toner said he didn't know.

"I'll try my best to get details about that," he said. He said the problem there is that the government generally doesn't want to reveal entities that help the U.S. make these payments, since the U.S. has no direct financial relationship with Iran.

But he said he also didn't know who received the payment.

"I believe it was Iranian officials, Iranian government officials, I don't know particularly who individually it was," he said.

When asked if anyone in the administration knows who was paid, he said he was "certain" that some in the U.S. knew, and said he just didn't have that information.

Toner explained that while the deal to complete the Iran nuclear deal and the deal to free U.S. hostages in Iran were separate, there were "snags" that delayed the completion of these agreements at the same time.

Because of those "snags," which he didn't detail, Toner said it would have been "imprudent" to simply hand over the money without waiting to ensure the hostages were released. Still, he said it wasn't "ransom," since it was money the U.S. owed Iran.

"But, in those final moments, it was decided that we were certainly going to use it as leverage, and that particular moment, until our citizens were back on a plane and safely out of Iranian airspace," he said.

But the White House seems to still disagree that it was "leverage" at all. At the White House briefing, spokesman Josh Earnest stressed that he never used that term, and that reporters should ask " someone else" who might have used the term.