U.S. President Donald Trump lashed out on Thursday at Republican conservatives who helped torpedo healthcare legislation he backed, escalating a feud within his party that jeopardizes the new administration’s legislative agenda. Trump threatened to try to defeat members of the Freedom Caucus – a bloc of conservative Republicans in the House of Representatives – in next year’s congressional elections if they continued to defy him. “The Freedom Caucus will hurt the entire Republican agenda if they don’t get on the team, & fast. We must fight them, & Dems, in 2018!” Trump wrote on Twitter on Thursday morning. He later singled out three Freedom Caucus members by name, U.S. Representatives Mark Meadows, Jim Jordan and Raul Labrador. “If @RepMarkMeadows, @Jim_Jordan and @Raul_Labrador would get on board we would have both great healthcare and massive tax cuts & reform,” he said in one tweet. “Where are @RepMarkMeadows, @Jim_Jordan and @Raul_Labrador? #RepealANDReplace #Obamacare,” he asked in another. House conservatives fought back. Labrador, one of the founders of the Freedom Caucus, urged Trump in a tweet to “Remember who your real friends are. We’re trying to help you succeed.” “Most people don’t take well to being bullied,” said Representative Justin Amash, who compared Trump’s approach to what a child does when he wants to “get his way.” Trump’s deteriorating relationship with Republican House conservatives could make it harder for him to pass his legislative agenda, which includes rewriting the U.S. tax code, revisiting a healthcare overhaul and funding construction of a wall along the U.S. – Mexican border.