Drug companies will likely have tens of millions of doses of coronavirus vaccines in the early part of next year, with production ramping up to a billion doses by the end of 2021. 

That's according to Dr Anthony Fauci, the top US infectious diseases official, who spoke to Reuters on Wednesday. 

Dr Fauci said he is hopeful the world could get past the pandemic that has claimed more than 700,000 lives worldwide by the end of next year with the help of a vaccine. 

He said he has not seen any pressure from the White House to announce a successful vaccine close to the 3 November election in the hopes of boosting President Donald Trump's re-election chances. 

Dr Fauci said health regulators have promised "they are not going to let political considerations interfere" with the approval of a Covid-19 vaccine and that "safety and efficacy" will be primary considerations. 

The interview with Reuters came on the same day President Trump told Fox News that the virus is "going away. It will go away like things go away". 

Dr Fauci offered a more mixed assessment, saying some parts of the country had done well in containing the spread of the virus, while others were "on fire". 

He characterized the varying responses to the virus as "disjointed" - owing to the size and the diversity of the nation. 

"I hope, and feel it's possible, that by the time we get through 2021 and go around for another cycle that we'll have this under control," he said. 

Earlier, it was announced that the US government had made a new $1 billion investment in a Covid-19 vaccine being developed by Johnson & Johnson, guaranteeing 100 million doses.

J&J, via its subsidiary Janssen, had already received $456 million in March.

The new money will allow the company to ramp up production so that doses are ready for shipping if and when the drug receives regulatory approval.

The US government also has the option to acquire additional doses sufficient to vaccinate 300 million people.

With the latest deal, President Donald Trump's administration has spent $9.4 billion on vaccine agreements, with five companies agreeing to provide at least 700 million doses, according to an AFP tally.

These deals, under Operation Warp Speed, foresee launching production in parallel with clinical trials, with the government taking the financial risk away from the private sector.

The US has also spent billions on building manufacturing sites, on companies that make syringes and vials, and on the development of treatments.

Washington has bought up almost all stock of the antiviral drug remdesivir that will be produced until September.

The medicine is the first treatment with proven benefit against Covid-19.

It comes as Canada signed an agreement for undisclosed financial terms with Pfizer Canada and BioNTech SE for 100 million doses of their experimental vaccine in 2020, and more than one billion in 2021, under "Project Lightspeed".