The Republican chairs of the House and Senate Armed Services committees issued a joint statement Wednesday criticizing the idea of the U.S. drastically changing its military combatant command structure, saying they “will not accept” those changes without coordination with Congress and other agencies.

The statement marks one of the first major instances of Republican lawmakers pushing back on President Trump in his second term.

House Armed Services Committee Chair Mike Rogers (R-Ala.) and Senate Armed Services Committee Chair Roger Wicker (R-Miss.) responded to an NBC News article published Tuesday that said the Pentagon is considering giving up its role as NATO’s supreme allied commander Europe (SACEUR) as part of restructuring of commands and headquarters.

“U.S. combatant commands are the tip of the American warfighting spear. Therefore, we are very concerned about reports that claim [the Defense Department] is considering unilateral changes on major strategic issues, including significant reductions to U.S. forces stationed abroad, absent coordination with the White House and Congress,” the two chairs said.

“We support President Trump’s efforts to ensure our allies and partners increase their contributions to strengthen our alliance structure, and we support continuing America’s leadership abroad. As such, we will not accept significant changes to our warfighting structure that are made without a rigorous interagency process, coordination with combatant commanders and the Joint Staff, and collaboration with Congress. Such moves risk undermining American deterrence around the globe and detracting from our negotiating positions with America’s adversaries,” they continued.

The statement indicated that the chairs of the powerful committees, who oversee the crafting of annual military and defense authorization bills, could use the power of the purse and other legislative tools to combat such a change, should the Trump administration move forward with it.

The U.S. has had a four-star general oversee NATO military operations in Europe for 75 years, NBC reported. The current SACEUR, Army Gen. Christopher G. Cavoli, is also the head of U.S. European command and has overseen support to Ukraine.

Updated March 20 at 5:30 a.m. EDT