Anthony Fauci says US has 'serious problem' as virus cases surge

America's top infectious diseases expert has warned the United States is facing a "serious problem" from a resurgent coronavirus as the illness puts the brakes on reopening two of the country's largest states.

"We are facing a serious problem in certain areas," leading US immunologist Anthony Fauci said at the first briefing in two months by the White House's Coronavirus Task Force.

"The only way we're going to end it is by ending it together," he said of the outbreak.

The US is recording more than 30,000 cases daily. With nearly 125,000 lives lost, it has by far the highest confirmed death toll in the world.

Texas had been among the most aggressive states in easing curbs but its strategy has backfired with the nation's second most populous state seeing several daily records in the number of new infections.

"It is clear that the rise in cases is largely driven by certain types of activities, including Texans congregating in bars," Governor Greg Abbott said.

Texas and Florida closed bars and reimposed other curbs on Friday as the number of infections in the US hit a single-day record with increases in 16 states, mostly in the south and west.

Meanwhile, the WHO on Friday called for another $27.9 billion in donations to speed up the development and production of tests, vaccines and other treatments, part of its ACT accelerator plan to pool international resources.

About $3.4 billion has already been pledged, the global body said ahead of a major fundraising event in Brussels by the EU Commission on Saturday that will feature performances by celebrities including Shakira and Justin Bieber.

More than 490,000 people worldwide have now died from the virus and the number of cases is expected to reach 10 million in the next week, according to an AFP tally.