The top United States official on infectious diseases, Anthony Fauci, said on Thursday that people could not get tests for the deadly coronavirus easily and the US testing system is not meeting the country's needs.

"The system is not really geared to what we need right now ... That is a failing. Let's admit it," Fauci told a House panel. "The idea of anybody getting it easily the way people in other countries are doing it, we're not set up for that. Do I think we should be? Yes. But we're not."

New York and Washington, the states hit the hardest by the coronavirus outbreak, are struggling to make testing for the virus widely available, and local officials estimate it could take weeks more to reach peak testing capacity.

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While over 1,270 people have been confirmed to have the virus in the United States - and at least 38 have died - according to official data, experts estimate the real number of cases may be far greater.

An unidentified flaw in test kits distributed by the federal government in February, which gave some false results, has set the country back in testing for the virus and containing an outbreak that has infected more than 121,000 people worldwide.

Boosting testing is crucial, disease experts say, to assessing the scope of the US outbreak and identifying where it is spreading most rapidly.

Vice President Mike Pence said on March 4 that roughly 1.5 million tests would be available by the end of that week, while President Donald Trump told reporters on Friday that "anyone who wants a test, gets a test".

But more than a week later, the ramp-up of creating testing kits has been much slower due to regulatory hurdles at the federal and state level, as well as logistical and technical challenges, according to healthcare providers, public health officials and test makers.

Nowhere illustrates the constraints on testing more than an outbreak at the Life Care Center nursing home in Kirkland, Washington, which alone accounts for 19 of 24 coronavirus-related deaths in the state.

Despite huge concern over how quickly the virus could spread there, about 150 of the 180 staff have not been tested. Life Care Center spokesman Tim Killian said the problem was a lack of kits to test employees.

Workers from a Servpro disaster recovery team wearing protective suits and respirators are given supplies as they line up before entering the Life Care Center in Kirkland, Washington [Ted S Warren/AP Photo]

Vanessa Phelps, whose 90-year old mother is a resident at the nursing home, was tested twice for coronavirus in a single week because she had been a frequent visitor. She cannot understand why all people affiliated with Life Care have not undergone testing.

"If they don't test everyone, one worker could still have it and be passing it around because people are still dying," said Phelps, who ultimately tested negative.

The state has increased capacity to about 1,000 tests a day at the University of Washington School of Medicine, and local officials say they are ready to help.

President Trump has been accused of initially downplaying the threat of the virus.

Under pressure, Trump announced on Wednesday that he was banning travel to the US from most of Europe beginning on Friday, causing anger and confusion across Europe.