A third of the Senate wrote to U.S. Ambassador to the United Nations Linda Thomas Greenfield on Thursday, urging her to bring a resolution before the United Nations Security Council designating and sanctioning Hamas as a terrorist organization.

The letter, led by Sens. James Lankford (R-OK) and Jacky Rosen (D-NV), comes amid criticism within the U.S. of some top U.N. officials for failing to strongly and unequivocally condemn Hamas and its attack on Israel on Oct. 7.

The U.N., the letter notes, has previously sanctioned other terrorist groups such as Al Qaeda and ISIS — although the prospect of sanctioning Hamas is likely to be difficult in the current geopolitical environment, given the apparent ties between Hamas leadership and Russia, which holds veto power on the Security Council.

The letter argues that Hamas’ “actions, tactics, and stated goals are in many ways indistinguishable” from those of U.N.-sanctioned groups, and that failing to sanction Hamas “risks eroding the U.N.’s credibility in response to one of the worst terrorist attacks in history.”

The letter argues that the lack of global sanctions allows Hamas to avoid U.S. sanctions, access the international financial system and solicit charitable donations, as well as allows Hamas to misappropriate humanitarian aid meant for civilians in Gaza. Much of the humanitarian aid to Gaza is provided through United Nations channels.

“Hamas’ reign of terror is not just an Israeli problem, but one that impacts us all,” the letter reads, highlighting that Hamas has taken hostages from 25 countries around the world.

The letter was co-signed by Sens. Kevin Cramer (R-ND), Maggie Hassan (D-NH), Thom Tillis (R-NC), Alex Padilla (D-CA), John Barrasso (R-WY), Cory Booker (D-NJ), Joni Ernst (R-IA), Kyrsten Sinema (I-AZ), John Boozman (R-AR), Rick Scott (R-FL), Mark Kelly (D-AZ), Jerry Moran (R-KS), Bill Hagerty (R-TN), Marco Rubio (R-FL), Mike Braun (R-IN), Chuck Grassley (R-IA), Cynthia Lummis (R-WY), Susan Collins (R-ME), Cindy Hyde-Smith (R-MS), Dan Sullivan (R-AK), Shelley Moore Capito (R-WV), Mike Crapo (R-ID), John Thune (R-SD), Deb Fischer (R-NE), John Kennedy (R-LA), Lindsey Graham (R-SC), Katie Britt (R-AL), Pete Ricketts (R-NE), Marsha Blackburn (R-TN), Steve Daines (R-MT) and Ted Budd (R-NC).