House Foreign Affairs Committee Chairman Ed Royce, R-Calif., on Wednesday demanded that Secretary of State John Kerry explain a $1.7 billion debt that the U.S. paid to Iran last month, which some Republicans suggest was a "ransom" payment designed to secure the coinciding release of five American prisoners held in the country, reported The Washington Post.

Royce wrote in a letter to Kerry that the State Department's failure to consult with his committee before paying out the settlement to Iran, along with timing of the settlement payment, "has led some to express concern that the payment represents a de facto 'ransom' for the release of American hostages."

Kerry announced on Jan. 17 that the U.S. would repay Iran a $400 million debt along with $1.3 billion in interest to settle a 1981 suit related to arms payments, according to AFP. The announcement came the same day that Iran released four Americans from prison and one day after the international nuclear deal was implemented.

"The Department had ample opportunity to seek Congressional input on this matter. Yet, it never raised this potential financial settlement with the Committee," Royce wrote. "It is unclear how this $1.7 billion payment is in the national security interests of the United States."

Royce asked Kerry to provide by Feb. 17 a list of all U.S. individuals who negotiated with Iran about the settlement agreement, the prisoner release and the nuclear deal. He also asked Kerry for a detailed timeline of payment negotiations between the U.S. and Iran, an explanation of how the $1.3 billion interest payment to Iran was calculated and a legal analysis of the dispute, according to Fox News.

After the settlement was made, Obama defended the amount by saying that a one-time payment was better than letting it accumulate more interest, and insisted it was "much less than the amount Iran sought."

State Department spokesman John Kirby confirmed to Reuters that Kerry received Royce's letter and planned on responding soon.

"We can confirm receipt of Chairman Royce's letter, and as with all Congressional correspondence, we'll respond as appropriate," Kirby said.