U.S. Sens. Shelley Moore Capito (R-WV) and Todd Young (R-IN) joined 18 of their Republican colleagues in telling President Joe Biden that they will not support a treaty that proposes global lists to restrict the production or use of chemicals, plastics, or plastic products or that requires new domestic authority.

The senators reached out to Biden just as talks at the United Nations Intergovernmental Negotiating Committee entered their final phase last week.

“The administration has changed the U.S. negotiating positions to address plastic pollution,” wrote the senators in a Nov. 14 letter sent to Biden. “It is unfortunate the administration appears to have succumbed to pressure from extremist environmental activists and now supports constraints on manufacturing and the development of target lists that identify chemicals and plastic products to be banned around the world in the potential treaty.”

The senators pointed out that throughout the negotiating process, the United States positioned itself to broker an agreement that not only seizes upon a historic opportunity to end plastic pollution in the environment, but one that also bolsters American manufacturing by supporting innovative new product designs and recycling technologies.

“This last-minute change in U.S. policy could sabotage years of positive collaboration and progress in brokering a treaty that ends plastic pollution, unlocks innovation, and, importantly, that could be ratified by the U.S. Senate,” they wrote.

The policy shift also harms the United States’ reputation in the negotiations, according to their letter, in which the lawmakers said it would be wise to reconsider the shift and ignore the calls of extremists who want to undermine U.S. manufacturers and American jobs.

“The world will need U.S. leadership in ending plastic pollution. A treaty that fails to gain the support of two thirds of the Senate will embolden countries like China who leak significant amounts of plastic waste into the environment,” the senators concluded. “Any agreement that includes provisions harmful to American manufacturing and jobs, or that unnecessarily drives up the costs to American consumers of food, electronics, vehicles, and other critical products, will not receive Senate ratification.”

The letter was led by U.S. Sen. Jim Risch (R-ID), ranking member of the U.S. Senate Foreign Relations Committee, and also included signatures from U.S. Sens. Bill Cassidy (R-LA), Marsha Blackburn (R-TN), Thom Tillis (R-NC), and Roger Wicker (R-MS).

The fifth session of the Intergovernmental Negotiating Committee to develop an international legally binding instrument on plastic pollution, including in the marine environment, known as INC-5, will be held from Nov. 25 to Dec. 1 in Busan, South Korea.