US President Donald Trump urged Republicans to "just repeal" the Obamacare and start over with a new plan, following opposition from conservative senators, who seemed unable to agree on an alternative proposal.

"Republicans should just REPEAL failing ObamaCare now and work on a new Healthcare Plan that will start from a clean slate. Dems (Democrats) will join in!," Trump tweeted late Monday.

The new health care bill proposed by the Trump government was left earlier on Monday with no apparent possible progress in the Senate after two other Republican lawmakers announced their opposition to the proposal, leaving the party a minority in the Upper House, reports Efe news.

The senators who opposed the proposal on Monday were Mike Lee and Jerry Moran, joining Susan Collins and Rand Paul as the four Republicans who have turned their backs on the proposal that the Trump government was trying to push to replace Obamacare.

In addition to the four opposing Republicans, several other senators such as Ron Johnson also expressed doubts about the new proposal.

Lee and Moran announced their opposition after the Republican Senate leadership decided to postpone its vote scheduled for this week due to the absence of Senator John McCain, who is recovering from eye surgery.

With the opposition of the four Republican and 48 Democratic senators against the repeal of Obamacare, the votes in favour of the new proposal would be below 50, the amount required to approve the bill.

This is the second proposal by the Republicans taken to the Senate, after the party's more conservative and moderate senators previously rejected the first proposal in June.

Like the previous proposal, the second bill proposed strong cuts in the Medicaid programme, which offers funding for medical services to people with low income in the US – a measure that was opposed by centrist Republican senators.

The new bill provided approximately $70 billion in additional funds that the states could use to help reduce health insurance premiums, keep medical costs down, and make health care more affordable.

It also included an amendment that allowed insurers to offer plans that did not comply with all Obamacare regulations, including the obligation related to pre-existing conditions

Democrat Senator Charles Schumer said this "second failure" of the Republicans to pass their own law proved that "the core of this bill is unworkable" and invited them to work together on a lasting law that would lower premiums and improves the system.

According to the non-partisan Congressional Budget Office (CBO), this bill would cause between 22 and 24 million people to lose their healthcare coverage within the next 10 years.