The State Department is still refusing to discuss the details of a covert payment worth $400 million to Iran that coincided with the release of four American hostages from Iran in January.

"I'm still frankly not prepared to talk about the mechanics," State Department spokesman Mark Toner told reporters Wednesday. "There's very little news to this."

The payment, which was sent to Iran in a cargo plane filled with foreign currency, was the first installment of a $1.7 billion legal settlement between the U.S. and Iran for a decades-old arms deal.

The administration has said that the payment, the hostage exchange, and the implementation of the Iran nuclear deal coincided by chance.

Toner reiterated that claim Wednesday.

"These were three very separate efforts," he said. "It was not a quid pro quo. It was not a ransom. What you saw was the culmination, as I said, of several lines of effort."

Officials have refused to discuss how the payment was made, other than that it did not occur in U.S. dollars, or when it was made, despite inquiries from lawmakers.

Toner acknowledged the difficulties that Iran's isolation from the financial system, including its inability to access the U.S. dollar, presented for the shipment.

"Iran was at that time ... relatively disconnected form the international financial system, and so that raised certain challenges in getting them their money," he said. "It couldn't be done over wire transfers, or any … of the financial methods that are commonly used to transfer large sums of money."

For these reasons, Toner said, the U.S. was "forced to get a little creative" in how it transferred the payment.

Critics have expressed concern that Iran would use the money to fund the Lebanese militia Hezbollah or the Assad regime in Syria. Toner said that the Islamic Republic does not seem to be using the payment for terrorist activities.

"So far, what they've used the settlement for has not been for any nefarious activities," Toner said. "In fact, it's been directed toward development projects, infrastructure projects."

Since the January payment, the Islamic Republic has detained at least two Americans.