Rubio cited a Wall Street Journal article reporting that the biggest enticement for Iran to free four American hostages in January wasn't the widely reported release of $1.7 billion frozen by Washington since the 1979-80 hostage crisis.
Instead, according to the Journal, the U.S. government lifted sanctions that had blocked Iran from procuring ballistic missiles eight years earlier than allowed under the 2015 nuclear deal Tehran and Washington sealed.
"President Obama promised (that) the United States would maintain and enforce sanctions on Iran's ballistic missile activities," Rubio said Friday. "Today we learned he secretly agreed -- eight years early -- to lift sanctions on an Iranian bank the U.S. Treasury Department described as the financial linchpin of Iran's missile-procurement network."
Ryan also criticized the recently revealed provision freeing Iran to start buying ballistic missiles.
"It now appears that on the same day American hostages were freed from Iran, the administration not only agreed to the $1.7 billion cash ransom payment, but violated a key term of the nuclear deal by prematurely lifting ballistic missile sanctions."
Pressed by reporters at a briefing, State Department Deputy Spokesman Mark Toner said the United States had "conducted a very thorough review" before deciding to lift the sanctions on the banks.
Asked directly whether the review had determined that the banks were no longer tied to Iran's missile procurement, Toner responded: "Yes, I mean that's exactly right. That they were no longer carrying out actions that we believed were linked to, or linked them to, the ballistic-missile program."
He added that "we continue to have concerns about Iran's ballistic-missile program."