Republicans in the US House and Senate slammed the Biden administration for the substance and the timing of a $6 billion prisoner swap deal with Iran announced on Monday, the anniversary of the Sept. 11, 2001, terrorist attacks.

Sen. Tom Cotton (R-AR), a fierce critic of the Biden administration’s policy toward Iran, decried the agreement as “shameless,” noting that US President Joe Biden had used the same anniversary as his deadline for withdrawing all American soldiers from Afghanistan in 2021.

“First Joe Biden used 9/11 as an excuse to flee Afghanistan. Now he desecrates this day by paying ransom to the world’s worst state sponsor of terrorism. Shameful,” Cotton wrote on Twitter.

The US intelligence community has consistently assessed that Iran is the world’s foremost state sponsor of terrorism.

Rep. Mike Lawler (R-NY), meanwhile, noted that Monday’s announcement came as Biden commemorated the Sept. 11 anniversary from a US airbase in Alaska, asking, “What the hell are they thinking?”

“Clearly the fresh air in Alaska has done little to improve the president’s decision-making,” Lawler said in a statement. “This announcement, on this day of remembrance, is beyond tone deaf.”

The US State Department informed Congress on Monday that it had issued a sanctions waiver to allow the transfer of $6 billion in Iranian funds from South Korea to Qatar, a step needed to carry out a previously announced US-Iran prisoner swap. The deal will allow five US citizens to leave Iranian custody in exchange for the money and the release of five Iranian prisoners held by the US.

US Secretary of State Antony Blinken has said the $6 billion will be transferred to “restricted accounts” where the funds will be available to the regime only for humanitarian trade and not terrorism.

The Biden administration has also insisted that the prisoner negotiations with Iran are a separate track from negotiations on Iran’s nuclear program, but Republicans have questioned whether an “understanding” or other informal agreement has been reached over Iran’s nuclear enrichment.

Sen. Ted Cruz (R-TX), for example, accused the administration of having already made a deal over Iran’s nuclear program without informing Congress.

“President Biden has established a secret nuclear deal with the Iranian regime that is being kept from Congress and the American people,” Cruz said in a statement about the prisoner deal.

“The Biden administration must keep their deal secret because if they disclosed it, the law requires them to come to Congress and defend it, and this appeasement is utterly indefensible. Instead they will continue lying about their policies until Congress forces them to do otherwise.”

In June, Rep. Michael McCaul (R-TX), chairman of the House Foreign Affairs Committee, wrote a letter alerting the Biden administration that even an informal agreement or understanding with Iran would have to be reviewed by Congress under the Nuclear Agreement Review Act of 2015 (INARA).

“This definition makes clear that any arrangement or understanding with Iran, even informal, requires submission to Congress,” McCaul’s letter said. “I urge the administration to remember that US law requires that any agreement, arrangement, or understanding with Iran needs to be submitted to Congress pursuant to INARA.”

While the Biden administration has denied that any such understanding about Iran’s nuclear program exists, Iran has slowed its rate of production of 60 percent enriched uranium in a move that some Western diplomats have hoped could be part of a “de-escalation” with Iran.

Despite those hopes, a recent analysis of reports from the United Nations’ nuclear watchdog, the International Atomic Energy Agency, concluded that Iran’s breakout time to a nuclear weapon has actually shrunk. According to the assessment, Iran could have enough material for a nuclear weapon in as little as 12 days.