The coronavirus outbreak could reach its peak in the United States this week, a top US health official said on Monday, pointing to signs of stabilisation across the country.

The US, with the world's third-largest population, has recorded more deaths from COVID-19 than any other country, more than 22,000 as of Monday, according to Johns Hopkins University.

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About 2,000 deaths were reported for each of the last four days in a row, the largest number of them in and around New York City. Experts say official statistics have understated the actual number of people who have succumbed to the respiratory disease, having excluded coronavirus-related deaths at home.

"We are nearing the peak right now," Robert Redfield, director of the Centers for Disease Control and Prevention (CDC) told NBC's Today programme. "You'll know when you're at the peak when the next day is actually less than the day before."

A little less than half of the coronavirus deaths in the US have occured in New York state.

The death toll in the state topped 10,000 on Monday, with hospitals seeing 2,000 new patients a day, officials said.

The state tallied 671 new deaths on Sunday. It was the first time in a week daily toll dipped below 700. Still, the Governor Andrew Cuomo noted people are still dying at a “horrific level of pain and grief and sorrow”.

Despite the grim numbers, Cuomo said there are still reasons to remain hopeful.

"I think you can say the worst is over," Cuomo said on Monday.

Sweeping stay-at-home restrictions to curb the spread of the disease, in place for weeks in many areas of the country, have taken a painful toll on the economy, raising questions over how the US can sustain business closures and travel curbs.

A message of thanks to healthcare workers and others is seen displayed on screens beneath the New Year's Eve Ball atop the One Times Square building in Manhattan during the outbreak of the coronavirus disease (COVID-19) in New York City, New York [Mike Segar/Reuters]

The new numbers from New York came as President Donald Trump retweeted a call to fire Dr Anthony Fauci after the country's top expert on infectious diseases said lives could have been saved if the country had shut down sooner during the novel coronavirus outbreak.

The retweet fuelled speculation Trump was running out of patience with the popular scientist and could fire him. The White House on Monday did not comment on Trump's retweet. Many online defended Fauci, who has become one of the US's most trusted voices on the coronavirus.

Easing restrictions?

On Sunday, a Trump administration official indicated May 1 was a potential date for easing the restrictions while cautioning that it was still too early to say whether that goal would be met.

Redfield refused to give a timeframe for the reopening of the US economy and praised social-distancing measures that he said helped curb the mortality rate.

"There's no doubt we have to reopen correctly," Redfield said. "It's going to be a step-by-step gradual process. It's got to be data-driven."

For his part, Trump on Monday tweeted it was his decision when to reopen the economy, but that he is "working closely" with state governors.

"A decision by me, in conjunction with the Governors and input from others, will be made shortly," he said.

A man crosses a nearly empty Fifth Avenue in midtown Manhattan during the outbreak of the coronavirus disease (COVID-19) in New York City [Mike Segar/Reuters]

Nancy Pelosi, speaker of the US House of Representatives, cautioned that the country was not prepared to end the shutdown.

"We all desire an end to the shutdown orders so we can get Americans back to work and back to normal," Pelosi said in a statement. "However, there is still not enough testing available to realistically allow that to happen."

This week Congress will work on further measures to soften the blow of the pandemic. Democrats want to add money for other anti-coronavirus efforts to a measure targeted at small businesses, including funding for rapid national testing and personal protective equipment.

"It cannot wait," Pelosi said.