Image copyright Getty Images Image caption Repealing and replacing Obamacare was a centrepiece to Mr Trump's presidential campaign

President Donald Trump has ratcheted up pressure on Senate Republicans to pass their proposed healthcare bill before returning home for August holidays.

"I cannot imagine that Congress would dare leave Washington without a beautiful new Healthcare bill fully approved and ready to go!" he tweeted.

But lawmakers remain split on passing a measure to overhaul former President Barack Obama's signature health law.

Mr Trump vowed to repeal the law, known as Obamacare, during his 2016 campaign.

Arizona Senator John McCain told CBS programme Face the Nation on Sunday that he believes the Republican bill is "probably going to be dead".

But the Trump administration adopted an optimistic tone.

White House chief of staff Reince Priebus told Fox News Sunday the president expected the Senate to approve a healthcare bill either before the start of lawmakers' August recess "or maybe a little bit into" the summer break.

Media playback is unsupported on your device Media caption Trump's battles with Obamacare - in his own words

Congress returned to Washington on Monday as a new survey highlighted the number of Americans without health insurance has grown by some two million this year, according to the Gallup-Sharecare Well-Being Index.

The Better Care Reconciliation Act of 2017, which would roll back parts of the 2010 Affordable Care Act and cut the tax increases that fund it, has faced mounting challenges.

Senate Majority Leader Mitch McConnell announced late last month lawmakers would delay a vote on the measure until after the 4 July holiday recess.

Liberal groups held protests to express their frustrations over the bill while lawmakers were home for the bank holiday last week.

Eight Republican senators had announced they would oppose the bill and the party can only afford to lose two votes to pass it in the upper chamber.

A version of the bill passed in the House of Representatives in May after facing a similar delay.

Hardline conservatives like Ted Cruz and Rand Paul have said they will not support the legislation, arguing the measure does not go far enough to dismantle the law, while moderate Republicans say the bill will harm some of their vulnerable constituents.

The non-partisan Congressional Budgetary Office (CBO) found the bill would strip 22 million Americans of health insurance over the next decade.

The 142-page Senate draft phases out the expansion of Medicaid, a government health programme for low-income Americans, and imposes deep cuts to the policy.

The bill also gives states more latitude in requiring insurers to provide essential health benefits guaranteed under Obamacare, including emergency and maternity care and mental health services.

More than 20 million people gained healthcare coverage under Obamacare.

Senator Cruz has proposed an amendment that would allow health insurers to sell cheaper, basic plans as long as at least one complies with Obamacare regulations, providing a loophole to the requirement that insurance companies charge sick and healthy consumers at the same rate.

Mr Cruz and other conservatives argue it will help lower premiums for healthy Americans, but opponents say it strips protections for sick people and those with pre-existing conditions.

A version of the bill with the Cruz amendment is being scored by the CBO.