US President Donald Trump’s administration has refused to reopen Obamacare exchanges to allow millions of laid-off workers to get health insurance, despite COVID-19 cases rising in large numbers in the US.

Trump has planted a timebomb under Obamacare, issuing a notice late on Thursday night that scraps vital federal subsidies underpinning the current healthcare system.

The Obamacare enrollment period ended months ago, but millions of people have filed for unemployment since the coronavirus crisis began. Though some Democratic states have reopened their insurance marketplaces, the Trump administration oversees enrollment for the vast majority of states.

The Trump administration sought to lay the blame for the current crisis in healthcare on former president Barack Obama, claiming the federal subsidies, known as “cost-sharing reduction payments”, were unlawful and “yet another example of how the previous administration abused taxpayer dollars and skirted the law to prop up a broken system”.

On Friday morning Trump claimed in a tweet that “the Democrats [sic] ObamaCare is imploding” and appeared to call on the Democrats to negotiate with him over healthcare legislation.

Though Trump refused, House Democrats are seeking to enhance Obamacare. The House bill aims to make Obamacare policies more affordable by bolstering federal premium subsidies. It would provide more assistance to those just above the poverty level, and it would limit monthly premiums to 8.5% of enrollees' income, instead of nearly 10% under the current law and more.