The Obama administration is refusing to provide documents to lawmakers seeking details about a controversial $400 million cash payment the U.S. made to Iran in January, according to exchanges viewed exclusively by THE WEEKLY STANDARD and congressional sources.

On Wednesday the State Department responded to a request for documents related to the cash transfer from the House Oversight Committee with a letter that reiterated the administration’s default stance on the controversy, but did not include any requested records.

The committee sent its request after the Wall Street Journal revealed earlier this month that the U.S. shipped $400 million in foreign currency, stacked in pallets in an unmarked cargo plane, to Iran around the time that the Islamic Republic released four American hostages.

The State Department's letter in response repeated previous administration claims that the cash transfer and prisoner exchange were not connected.

"Implementation Day of the [Iran nuclear deal], the release of several American citizens unjustly imprisoned in Iran, and the settlement of the Hague claim were all … resolved on their own merits," the letter states, referring to the legal settlement for a decades-old $1.7 billion arms deal with Iran gone awry, of which the $400 million represents the first installment.

Officials have for weeks claimed that the payment was not quid pro quo and that the timing of events was "coincidental." This claim has been broadly criticized by lawmakers and Iran watchers. The administration's position on the payment came under renewed pressure within a day of the State Department's response letter to the committee.

On Wednesday, the Journal reported that the cash transfer and prisoner release occurred in a "tightly scripted" exchange, where the delivery of the $400 million was delayed until American hostages held in Iran were "wheels up."

The next day, State Department spokesman John Kirby confirmed to reporters that the prisoner release and cash transfer were linked.

"You're saying that you wouldn't give [Iran] the $400 million in cash until the prisoners were released, correct?"

"That's correct," Kirby said.

Kirby also acknowledged that the administration had hidden the link.

"I certainly would agree that this particular fact is not something that we've talked about in the past," he said.

Kirby told reporters that the $400 million was used as "leverage" to retrieve the hostages, but continued to deny that the payment was quid pro quo since Iran was "going to get this money anyway."

The administration has long refused to disclose details about the payment, including the timing of it and how it was made, to reporters and lawmakers. State Department officials have insisted that they were upfront with Congress.

"I can assure you that we don't do anything without notifying Congress, regardless of what that may be," State Department spokesman Mark Toner said after the Journal story broke. "We always make Congress aware of whatever actions we're taking."

State sent a similar letter to House Foreign Relations Committee chairman Ed Royce in March, weeks after he asked for information about the payment. Unsatisfied with the administration's response, the California congressman sent a second letter in June.