President Donald Trump barged into Senate Republicans’ delicate health care negotiations on June 30, 2017, declaring that if lawmakers can’t reach a deal they should simply repeal “Obamacare” right away and then replace it later on.

Mr. Trump’s tweet revives an approach that GOP leaders and the President himself considered but dismissed months ago as impractical and politically unwise. And it’s likely to further complicate Majority Leader Mitch McConnell’s task as he struggles to bridge the divide between GOP moderates and conservatives as senators leave Washington for the Fourth of July break without having voted on a health care bill as planned.

“If Republican Senators are unable to pass what they are working on now, they should immediately REPEAL, and then REPLACE at a later date!” Mr. Trump wrote.

The President sent his early-morning tweet shortly after Nebraska Republican Senator Ben Sasse appeared on Fox News Channel’s “Fox & Friends” to talk about a letter he had sent to Mr. Trump making that exact suggestion — a vote on repealing former President Barack Obama’s health law followed by a new effort at a working out a replacement.

Mr. Trump is a known “Fox & Friends” viewer, but Republican Senator Rand Paul of Kentucky also claimed credit for recommending the tactic to the President in a conversation earlier in the week.

“Senator Rand Paul suggested this very idea to the President,” said Mr. Paul’s spokesman Sergio Gor. “The Senator fully agrees that we must immediately repeal Obamacare and then work on replacing it right away.”

Either way, Mr. Trump’s suggestion has the potential to harden divisions within the GOP as conservatives like Mr. Paul and Mr. Sasse complain that Mr. McConnell’s bill does not go far enough in repealing Mr. Obama’s health care law while moderates criticise it as overly harsh in kicking people off insurance roles, shrinking the Medicaid safety net and increasing premiums for older Americans.

Mr. McConnell told reporters after an event on June 30, 2017 in his home State of Kentucky that the health care bill remains challenging but “we are going to stick with that path”. “It’s not easy making American great again, is it?” Mr. McConnell said.

Mr. McConnell has been trying to strike deals with members of both factions in order to finalise a rewritten bill lawmakers can vote on when they return to the Capitol the second week of July. Even before Trump weighed in, though, it wasn’t clear how far he was getting, and Mr. Trump’s tweet did not appear to suggest a lot of White House confidence in the outcome.

“McConnell’s trying to achieve a 50-vote Venn diagram between some very competing factions,” said Rodney Whitlock, a veteran health policy expert who worked as a Senate GOP aide during passage of the Democrats’ Affordable Care Act. “So what the president tweeted takes one side of that Venn diagram and pushes it further away, and actually puts on the table an option that will probably drive that group away from seeking compromise with the other side of the Venn diagram.”

Even before Mr. Trump was inaugurated in January, Republicans had debated and ultimately discarded the idea of repealing Obamacare before replacing it, concluding that both must happen simultaneously. Doing otherwise would invite accusations that Republicans were simply tossing people off coverage and would roil insurance markets by raising the question of whether, when and how Congress might replace Mr. Obama’s law once it was gone.

The idea also would leave unresolved the quandary lawmakers are struggling with now, about how to replace Mr. Obama’s system of online insurance markets, tax subsidies and an expanded Medicaid with something that could get enough Republican votes to pass Congress. House Republicans barely passed their version of an Obamacare replacement bill in May, and the task is proving even tougher in the Senate, where Mr. McConnell has almost no margin for error.

Moderates were spooked as the week began with a Congressional Budget Office finding that Mr. McConnell’s draft bill would result in 22 million people losing insurance over the next decade, only 1 million fewer than under the House-passed legislation which Mr. Trump privately told senators was “mean.” But conservatives continue to insist that the bill must go further than just repealing some of the mandates and taxes in Mr. Obama’s law.

“It’s distressing to see so many Republicans who’ve lied about their commitment to repeal,” Ken Cuccinelli, president of the Senate Conservatives Fund, said in a conference call on June 30, 2017.

Underscoring the fissures within the GOP, conservative group leaders on the conference call welcomed Mr. Trump’s suggestion but said it didn’t go far enough because it could open the door to a subsequent bipartisan compromise to replace Mr. Obama’s law. At the same time, a key House Republican, Representative Kevin Brady who chairs the Ways and Means Committee, rejected Mr. Trump’s suggestion, contending that it “doesn’t achieve what President Trump set out to do”.

“I really think the Senate’s approach certainly in the House of not simply repealing but to start to put into place the elements that can make health care affordable, that’s what the president set out to do,” Mr. Brady said in an interview on C-SPAN’s “Newsmakers” programme.