The US death toll from the Covid-19 pandemic surpassed 900,000 on Friday, according to the Johns Hopkins University coronavirus tracker.

The toll had hit 800,000 dead in mid-December, just a month and a half ago.

New cases linked to the Omicron variant are falling, but daily deaths are still rising, with an average of 2,400 now, according to government figures.

"Hospitalizations remain high, stretching our healthcare capacity and workforce to its limits in some areas of the country," said Rochelle Walensky, director of the Centers for Disease Control and Prevention.

Covid deaths usually occur a few weeks after patients get the virus, which explains why the spike in deaths occurs later than the spike in new cases.

"Today, our nation marks another tragic milestone -— 900,000 American lives have been lost to COVID-19," President Joe Biden said in a statement. "We pray for the loved ones they have left behind, and together we keep every family enduring this pain in our hearts."

Americans continue to die from Covid in large numbers because only 64 percent of the population is fully immunized, despite highly effective vaccines being widely available.

In his statement, Biden again urged Americans to get vaccinated.

"Vaccines and boosters have proven incredibly effective, and offer the highest level of protection," he said.

The United States has the most Covid deaths in absolute terms, ahead of Brazil and India, according to government figures.

The Covid pandemic has killed at least 5.7 million people worldwide since it began in December 2019, according to an AFP tally published on Friday.

But the World Health Organization says the actual toll could be two to three times higher.