President Donald Trump’s threats to impose blunt new tariffs on Mexico has unleashed a circular firing squad among Republicans in Congress.

A bloc of Senate Republicans is threatening to put up a veto-proof majority to block the tariffs if Trump moves forward by using his national emergency powers. But most House Republicans and another faction of GOP senators say their colleagues are making a mistake by undercutting the president on one of his signature issues.

“I’m disappointed that so many of my colleagues are quick to announce their opposition,” said Sen. Kevin Cramer (R-N.D.). “By so publicly rebuking the president’s strategy you undermine the very leverage that could end this thing quickly. That’s the irony to me.”