One of Donald Trump's most senior advisers has said she doesn’t understand why Democrats won’t support his repeal of the Affordable Care Act, known as Obamacare.

Kellyanne Conway said it was "unfortunate" that their rivals did not "want to support health care reform.”

“I think that that’s unfortunate because the president and senior staffers here have made very clear that we welcome Democratic votes in support of healthcare reform, tax reform, infrastructure, and other measures that are meant to benefit Americans," she told Fox News.

Mr Trump made reversing the act one of his key campaign pledges during the presidential election.

But when he introduced his flagship American Healthcare Act to replace it earlier this year, it was withdrawn by House Speaker after Paul Ryan, after it was clear that it would not obtain enough votes to be passed.

Not only did Democrats unanimously oppose it, but members of Mr Trump's own Republican Party also refused to back it, leading to an embarrassing defeat for the US leader.

Since the Affordable Care Act became law, the number of uninsured Americans has been halved, down to 8.8 per cent of the population.

Analysis by the Congressional Budget Office (CBO) found that Mr Trump's replacement would have left 24 million people uninsured by 2026.

The CBO also said that while it would have saved the government money, people's insurance premiums would have risen by between 15 and 20 per cent above the expected increase under Obamacare.

However, the President has said health care reform is back on the agenda.

It appears the White House is seeking a compromise deal to appease the hard-line conservative groups, such as the Freedom Caucus, who scuppered his first attempt.

Mr Trump recently claimed on Twitter that: "Talks on Repealing and Replacing ObamaCare are, and have been, going on and will continue until such time as a deal is hopefully struck."

At a conference earlier this week,he also claimed the Republicans were "doing very well on healthcare."