President Donald Trump heaped fresh pressure on US lawmakers Monday, July 10 to pass an unpopular health care reform bill before Congress goes on its August recess next month, AFP reports.

As Senators returned for work in Washington after a week off, Trump challenged fellow Republicans to make good on their signature campaign promise: repeal and replace "Obamacare," the reforms of his White House predecessor.

"I cannot imagine that Congress would dare to leave Washington without a beautiful new HealthCare bill fully approved and ready to go!" Trump wrote in an early morning tweet burst.

Both chambers will go on recess for more than five weeks beginning July 28.

Trump has made repealing and replacing the 2010 Affordable Care Act a centerpiece of his agenda, and last month expressed confidence that the Senate bill would be a "phenomenal" plan with "heart."

Senate Republican leader Mitch McConnell and aides crafted the new bill essentially in secret. When it was unveiled in late June it immediately faced internal dissent from conservative and moderate wings of the party, and McConnell could not muster enough support before the July 4th holiday week as he had hoped.

With Democrats united in opposition, McConnell needs the votes from 50 of the 52 Senate Republicans to get the measure passed.