'We must fight them': Trump threatens to back challengers to conservative Republicans if they don't 'get on the team'

President Donald Trump blasted the House Freedom Caucus on Thursday, threatening to back challengers to members of the conservative caucus that helped block the GOP healthcare bill last week.

"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.

Trump has increasingly lit into members of the conservative caucus for failing to support the American Healthcare Act, the president's and GOP leadership's replacement bill for President Barack Obama's signature legislative achievement, the Affordable Care Act.

Though he initially blamed Democrats for the failure of his bill, the president on Sunday said that the opposition party was "smiling" at Republicans' inability to repeal Obamacare.

He attacked the caucus again in a tweet Monday.

"The Republican House Freedom Caucus was able to snatch defeat from the jaws of victory. After so many bad years they were ready for a win!" Trump said.

Trump's repeated criticism of the caucus suggests he won't easily forget who sank his first major attempt to pass legislation.

The Daily Beast reported last week that Trump's chief political strategist, Steve Bannon, advised the president to keep a "s--- list" of lawmakers who opposed the bill, threatening future retribution.

In recent days, Trump has floated working with Democrats on healthcare legislation, a prospect at which GOP leadership has bristled.