Washington DC: US President Donald Trump on Thursday pledged to "crush" the coronavirus pandemic with a vaccine by the end of the year, as he accepted the Republican nomination for a second term.

"We are marshaling America's scientific genius to produce a vaccine in record time," Trump said. "We will have a safe and effective vaccine this year and together we will crush the virus."

Trump appears to have pinned his hopes on the swift emergence of a successful vaccine to both contain the country's still raging epidemic and revive his faltering re-election hopes.

The facility has been awarded a contract to mass produce an experimental vaccine developed by Novavax, as part of a multi-billion dollar government initiative dubbed Operation Warp Speed.

The plan involves investing heavily in leading pharmaceuticals to aid their development and manufacturing efforts, with the goal of delivering 300 million doses of vaccine by January 2021.

It's "never been done before, but we suspect it's going to work, and work very well," added Trump, who later donned a black mask and toured the lab.

The United States is by far the worst-hit country in the world, with more than 4.2 million confirmed COVID-19 cases and nearly 150,000 deaths.

Though the number of new cases has leveled off over the past few days, the US has failed to push its curve down as other nations have done through lockdowns and physical distancing.

Trump's latest comments confirmed that the administration believes that, in America's case, only a vaccine can help.

"It's not masks. It's not shutting down the economy. Hopefully, it is American ingenuity that will allow for therapies and vaccines to ultimately conquer this," White House chief of staff Mark Meadows told ABC News on Sunday.

The virus has also repeatedly penetrated Trump's inner circle, with O'Brien the latest and most senior White House aide to test positive.

The US has spent more than $6.3 billion since March to fund vaccine development efforts under Operation Warp Speed.