Donald Trump has sensationally sacked his defence chief and planned more rallies as president-elect Joe Biden warned of a “very dark winter” while forming a coronavirus taskforce.

As the US became the first country to reach 10 million infections  – with 237,000 deaths – Mr Biden said he would elevate scientists and public health officials to tackle the pandemic.

He welcomed Pfizer’s announcement of the COVID vaccine’s 90 per cent success rate but warned it would be “many months” before it was widely available and in the meantime another 200,000 Americans could die.

“We’re still facing a very dark winter,” Mr Biden said. “The challenge before us right now is still immense and growing.”

The task ahead of the Biden-Harris administration is unlike any other in our history.

In preparation, our transition will be led by experts, by science, and with character—ensuring that we will be ready to lead on Day One.

— The White House (@WhiteHouse) November 8, 2020

The taskforce includes whistleblower Rick Bright, an immunologist who said he was sacked under the Trump administration for raising early warnings about the coronavirus.

Meanwhile, Mr Trump still has not acknowledged defeat as he fights an array of lawsuits claiming unfounded election fraud as state officials said they were not aware of any significant irregularities.

Instead Mr Trump announced on Twitter the sudden sacking of Defence Secretary Mark Esper without explanation, and named his replacement as Christopher C. Miller, Director of the National Counterterrorism Centre.

“I am pleased to announce that Christopher C. Miller, the highly respected Director of the National Counterterrorism Center (unanimously confirmed by the Senate), will be Acting Secretary of Defense, effective immediately,” Mr Trump tweeted.

“Mark Esper has been terminated. I would like to thank him for his service.”

…Chris will do a GREAT job! Mark Esper has been terminated. I would like to thank him for his service.

— Donald J. Trump (@realDonaldTrump) November 9, 2020

CNN reports tensions between Mr Trump and Mr Esper had been long simmering to the point the defence chief had already drafted a letter of resignation before the election.

Mr Esper was said to have been particularly at odds with the president over the use of active-duty troops to quell public unrest such as the George Floyd riots.

While there has still been no sign of Mr Trump, his campaign spokesman Tim Murtaugh said the president planned to hold rallies to build support for his legal challenges.

Mr Trump will seek to back up his as yet unsubstantiated accusations of voting fraud by highlighting obituaries of dead people the campaign said had voted in the election, Mr Murtaugh said.

Mr Trump also announced teams to pursue recounts in several states. Experts said that effort, like his lawsuits, were unlikely to meet with success.

Joe Biden and Kamala Harris speak virtually with their new Covid-19 Advisory Council. Photo: Getty

The Biden-Harris team has launched a “transition” website outlining the Democrats’ key priorities they plan to begin working on as they prepare to take office in January.

As well as COVID-19, Mr Biden and vice president-elect Kamala Harris will focus on economic recovery, racial equity and climate change.

Their COVID response will emphasis mask-wearing, social distancing, contact tracing and handwashing.

However the transition cannot shift into high gear until the US General Services Administration, which oversees federal property, certifies the winner.

Emily Murphy, the Mr Trump appointee who runs the agency, has not yet done so and a GSA spokeswoman gave no timetable for the decision.

Until then, the GSA can continue providing Mr Biden’s team with offices, computers and background checks for security clearances, but they cannot yet enter federal agencies or access federal funds set aside for the transition.

The Biden campaign on Sunday pressed the agency to move ahead.

“America’s national security and economic interests depend on the federal government signaling clearly and swiftly that the United States government will respect the will of the American people and engage in a smooth and peaceful transfer of power,” the campaign said in a statement.

– with AAP