Azar made the remarks on Thursday while addressing a keynote speech at the Goldman Sachs Healthcare virtual event, reports CNBC News.

According to the top official, 'Operation Warp Speed', the administration's Covid-19 vaccine program, expects to have up to 100 million doses by the end of the year.

That's "enough to cover especially vulnerable populations" he said, adding: "We project having enough for every American who wants a vaccine by March to April 2021."

Azar said that the country was currently manufacturing doses for all six potential vaccines backed by President Donald Trump's government across more than 23 manufacturing facilities.

These includes vaccines from Moderna, Pfizer, AstraZeneca and Johnson & Johnson, which are all in late-stage testing.

According to the Health and Human Services Secretary, the US is also obtaining needles, syringes, bottles and other supplies needed for immunizations.

US health officials believe authorizing a vaccine for emergency use is appropriate in "only specific circumstances", where there are "sufficient amounts of vaccine already manufactured" , CNBC News quoted Azar as further saying.

Azar's remarks follows a sweeping plan unveiled by the Centers for Disease Control and Prevention (CDC) last month to make Covid-19 vaccines available to all Americans for free.

Under the plan, the CDC anticipates a coronavirus vaccine will initially be granted an emergency use authorization before a full formal approval.

The US continues to lead the world with the highest number of coronavirus cases and deaths.

As of Friday, the overall number of cases in the country reached 7,603,746, while the death toll stood at 212,716, according to the Johns Hopkins University.