Image copyright EPA Image caption Senate Majority Leader Mitch McConnell says senators had a "duty to act"

The US Senate has failed to pass a Republican proposal to repeal President Barack Obama's signature healthcare policy without replacing it.

The 45-55 vote marks the second defeat for Republicans aiming to pass a bill this week to undo the health policy.

The vote came a day after the Senate rejected a plan to repeal and replace the health law with a Republican plan.

Senators will now consider a "skinny" repeal, which would scale back some of the more controversial provisions.

The "skinny" plan would eliminate unpopular parts of Obamacare - the Affordable Care Act - including the individual mandate requiring all Americans to have health insurance coverage as well as a tax on medical devices.

If that measure passes, the Senate and House of Representatives would then be tasked with finalising a bill that could still change during negotiations.

If successful, the full House and Senate would again have to approve the measure.

Seven Republicans opposed the repeal-only plan on Wednesday, which included a two-year delay on a replacement in the hope of finding agreement before that time elapses.

The defeat is the latest blow for President Donald Trump, who put repealing Obamacare at the centre of his election campaign, and underscores sharp divisions within the Republican Party over a replacement plan.

A proposal to repeal and replace Obamacare with the Better Care Reconciliation Act (BCRA), a Republican plan that was crafted over last two months, collapsed on Tuesday night after nine Republicans voted against it.

Republicans have long railed against Obamacare as government overreach, criticising the system for introducing government-run marketplaces, where premiums have risen sharply for some people.

The party's proposed alternative included steep cuts to Medicaid, a healthcare programme for the poor and disabled.

And it removes Obamacare's individual mandate requiring all Americans to have health insurance or pay a tax penalty.

About 20 million people gained health insurance under former President Obama's Affordable Care Act.

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

Other attempts to replace Obamacare have failed in recent weeks due to Republican divisions.

In an early morning tweet on Wednesday, Mr Trump lambasted Republican Senator Lisa Murkowski of Alaska for opposing the party's plan, saying she "really let the Republicans, and our country, down yesterday. Too bad!"

Mrs Murkowski was one of two Republicans earlier on Tuesday to vote against allowing the debate on healthcare legislation reform to go forward.

But her party eked out a victory after Vice President Mike Pence cast the tie-breaking vote which allowed discussion to take place.

Media playback is unsupported on your device Media caption John McCain returned to the Senate to applause

Senator John McCain, who was recently diagnosed with an aggressive brain tumour, received a standing ovation as he returned to Congress to cast his "Yes" vote.

President Trump tweeted his thanks to the Arizona senator for playing "such a vital role" in the vote.

Six months of Trump