Congress is pursuing new legislation that would force the Obama administration to disclose details about a $1.7 billion taxpayer-funded payment to Iran that multiple sources have described as a "ransom payment" to the Islamic Republic, the Washington Free Beacon has learned.

The legislation, which comes on the one-year anniversary of the nuclear agreement with Iran, would force the administration to provide additional details about the payment and prohibit future taxpayer-funded payouts to Iran and other state sponsors of terrorism, according to the legislation.

The payment to Iran has been shrouded in mystery since January, when the administration announced that it had settled decades-old legal disputes with Iran. U.S. and Iranian officials have said the payment was part of an effort to free Americans held in Iran, though the administration has denied this.

Key documents and information about the payment have been withheld from Congress for months, despite multiple inquiries.

Sens. James Lankford (R., Okla.) and Deb Fischer (R., Neb.), who are spearheading the new bill, said U.S. taxpayers should be told why their money is being sent to the globe’s top sponsor of terrorist activities.

Recent reports indicate that Iran has already spent the $1.7 billion to expand its military resources.

"President Obama’s billion-dollar payment to Iran in January, which we now know will fund Iran’s military expansion, is an appalling example of Executive Branch governance," Lankford said in a statement provided to the Free Beacon.

"One year after the Iran Nuclear agreement, we still have the same concerns with Iran," he said. "Iran continues to spread terrorism and a radical Islamist ideology around the region. The bill Senator Fischer and I have introduced will provide the American public with necessary details of the dangerous billion-dollar payment to Iran and ensure that no taxpayer dollars are ever again used to fund the extremist and violent ambitions of rogue nations like Iran. Subsidizing Iran’s military is perhaps the worst use of taxpayer dollars ever by an American president."

Fischer also said that "hardworking American families have every right to see exactly how their tax dollars are being spent, especially when used to fund hostile enemies of the United States."

"More transparency," Fischer said, "leads to greater accountability and through this bill, we can hold our government to task for their actions. We should not be in the business of providing funds to state sponsors of terrorism."

The legislation would force the administration to pull back the curtain on the methods used to fund the $1.7 billion payment. It also would ban any future payments to state sponsors of terrorism such as Iran.

The payment was granted using a legal fund maintained by the Treasury Department that is used to pay out judgments made against the United States.

The Obama administration said the payment was part of an effort to settle decades-old disputes with Iran surrounding an arms deal that went sour. The United States ultimately paid Iran $400 million to resolve the dispute, as well as an additional $1.3 billion in interest.

Congressional attempts to obtain further information about the payout and circumstances surrounding it have been stonewalled by administration officials.

"Earlier this year, the administration announced a $1.7 billion settlement to a case that had been pending for 35 years before the [International Claims] Tribunal, claiming it was in the American public’s best interest to settle," Rep. Ileana Ros-Lehtinen (R., Fla.), one of the lawmakers spearheading a separate disclosure effort, told the Free Beacon in June. "But we’ve never seen the documents and we don’t know why a settlement was announced, conveniently, the day after restrictions were lifted on Iran’s Central Bank."