WASHINGTON • The United States is facing a "serious problem" as southern and western states experience a surge in coronavirus cases, leading government expert Anthony Fauci has warned.

"We are facing a serious problem in certain areas," said Dr Fauci, noting that while some places were faring far better than others, the entire country was "interconnected" and remained at risk.

"So people are infecting other people, and then ultimately you will infect someone who's vulnerable," Dr Fauci said.

"And that may be somebody's grandmother, grandfather, uncle, who is on chemotherapy and who's on radiation or chemotherapy, or a child who has leukaemia.

"We are all in it together, and the only way we're going to end it is by ending it together."

Dr Fauci was speaking on Friday at the first news briefing in two months by the coronavirus task force led by US Vice-President Mike Pence - who sought to strike a reassuring tone, telling Americans the situation was not comparable with the height of the crisis in the country's north-east, in March and April.

"We're in a much stronger place. The truth is we did slow the spread, we flattened the curve," Mr Pence said as he called on young Americans to follow social distancing guidelines but did not mention the wearing of masks.

Mr Pence later defended President Donald Trump's controversial decision to resume large campaign rallies despite the pandemic, saying Americans had a right to freedom of speech and assembly.

The task force briefing was called after a surge in new coronavirus cases in southern and western states, including Florida and Texas.

On Friday, both states announced measures to discourage people from meeting in groups, such as ordering bars closed or banning on-site alcohol consumption.

Wall Street stocks suffered their second rout in three sessions following the announcements, with major US indexes falling around 2.5 per cent or more to finish the week in the red.

Texas and Florida are two of the most populous states in the country and together are home to some 50 million people. Other southern and western states, including Arizona and Georgia, have also seen a big jump in cases.

Investor confidence in a US economic recovery is "being stymied by lingering Covid-19 concerns as new cases persist", analysts at the Charles Schwab brokerage said.

The US has recorded some 2.5 million coronavirus cases and over 127,000 deaths, more than anywhere else in the world.

Amid the spike in cases, Mr Trump cancelled a planned weekend visit to his golf resort in Bedminster, New Jersey.

The White House announced the scrapping of the trip on Friday just hours before he was due to board Air Force One, without offering any explanation.

White House spokesman Judd Deere said the cancellation was not related to New Jersey's requirement that visitors from states with high coronavirus infection rates self-quarantine for 14 days upon arrival.

The US President had visited one of the states with high rates, Arizona, earlier last week.

Later, Mr Trump said he was staying in Washington "to make sure LAW & ORDER is enforced".

"The arsonists, anarchists, looters and agitators have been largely stopped," he wrote on Twitter. "I am doing what is necessary to keep our communities safe - and these people will be brought to Justice!"

Mr Trump has pledged to take a hard line on anyone destroying or vandalising historical US monuments, as activism against racial injustice sweeps the country.

AGENCE FRANCE-PRESSE, REUTERS