The administration of President Joe Biden said Thursday it will strengthen coronavirus testing rules for those entering the United States amid concerns over the new Omicron variant, requiring all air travelers to provide a negative result within one day of their scheduled departure.

The announcement came amid signs of the Omicron variant seeping into the United States, with multiple cases detected in the state of New York and elsewhere after the first U.S. case was announced on Wednesday.

A sign promotes a COVID-19 testing location at Los Angeles International Airport on Dec. 1, 2021. (Getty/Kyodo)

The new COVID-19 testing protocol for international air travel will be put in place starting early next week. It is part of a series of actions the administration has planned to allow the nation to navigate the ongoing pandemic without the need to shut down schools and businesses.

Currently, non-U.S. citizens and those without residency rights arriving by air are required to be fully vaccinated and to test negative for the coronavirus within three days before boarding a flight to the United States.

For those who are not fully vaccinated but meet certain criteria such as citizens coming from a foreign country with limited vaccine availability, a negative COVID-19 test result is needed no more than one day before travel.

The new rules, however, will require all inbound international travelers to return a negative test within one day of departure globally, regardless of nationality or vaccination status, according to the U.S. government.

"This tighter testing timeline provides an added degree of public health protection as scientists continue to assess the Omicron variant," it added.

Mask-wearing will also continue to be required during international flights and other travel on public transport, as well as in transportation hubs such as airports or indoor bus terminals through March 18, according to the government.

The Biden administration also vowed to ramp up efforts to expand the availability of booster shots for additional protection for adults who have already received a single-dose COVID-19 vaccine or both shots of a two-dose inoculation, while expanding free at-home testing.

Although concerns are growing over the emergence of the new variant, U.S. health authorities are calling on the public to continue to follow existing recommendations, such as getting vaccinated and masking in indoor settings where people congregate.

The first case of the Omicron variant in the United States was announced on Wednesday, involving an individual in California who returned from South Africa on Nov. 22.

A second confirmed case was a Minnesota resident who traveled to New York City to attend a three-day anime convention showcasing Japanese pop culture that ended Nov. 21, according to the Minnesota Health Department.

Later Thursday, the New York state government announced it had confirmed five Omicron variant cases, including four in New York City. The fifth case, in Suffolk County on Long Island, was a woman who had recently traveled to South Africa.

"We still don't have specific information on how the vaccines are holding up or the boosters are holding up to this variant," New York Gov. Kathy Hochul told a press conference. "While this may be highly transmissible, at least from the early evidence...we want people to know that the early cases...are not life-threatening, they seem to be minor cases."

The United States has implemented a ban on the entry of foreign travelers from eight countries in southern Africa, after South Africa became among the first to report the strain, labeled a concern by the World Health Organization, last week.

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