WASHINGTON, March 10 (CNA) - The number of US cases of the novel coronavirus surged to more than 900 on Tuesday (Mar 10), according to an AFP tally, after public health experts criticised authorities for downplaying the epidemic and lagging behind in testing efforts.

At least 23 people have died and 959 people have been infected, according to Johns Hopkins University in the United States.

The rise is linked to an expansion in testing as the bulk of diagnoses have shifted from federal to state laboratories.

Epidemiologists have said faulty test kits coupled with a diagnostic strategy that initially targeted too few people allowed the disease to spread beyond US authorities' ability to detect it.

Writing in the Journal of the American Medical Association (JAMA) on Monday, academics from Johns Hopkins University and Stanford University said the failings had contributed to the virus taking root across the country.

Speaking at a White House briefing, Vice President Mike Pence defended the federal government's response and said that "a million tests are in the field." He added that more would be added as the government partnered with private companies.

According to the latest CDC figures, 8,554 tests had been performed as of Monday.

By way of comparison, South Korea, which announced its first case on the same day as the US, has tested more than 189,000 people, according to a report in the Business Insider.

The authors of the JAMA report wrote that the only test initially authorised was one developed by the CDC.

It relied on the same technology as one authorised by the World Health Organization (WHO) and deployed around the world - except that a fault meant the CDC kit was returning inconclusive results.

It was not until Feb 29, the date of the first US death and more than a month after the first confirmed US case, that the Food and Drug Administration lifted a ban on state laboratories developing their own kits based on the WHO's tests.