International arrivals will now have to take a Covid test within 24 hours of their departure to the US, regardless of vaccination status, as opposed to the previous 72-hour time allowance.
The new restrictions will be introduced “early next week”, according to an official statement from the White House.
The updated rules will apply to all passengers arriving into the country, whether international travellers or US citizens.
Even those who are fully vaccinated will have to comply. International travellers are currently only allowed into the States if they have received a full course of an approved Covid-19 vaccine.
“This tighter testing timeline provides an added degree of public health protection as scientists continue to assess the omicron variant,” reads the statement from the Biden Administration.
“The President will announce additional steps to strengthen the safety of international travel as we face this new threat – just as we have faced those that have come before it.”
The US took steps to restrict travel from the countries where omicron cases had been identified as spreading quickly on the the same day that the World Health Organization (WHO) recognised the new variant.
However, the country recorded its first omicron case on 1 December. The fully vaccinated traveller had arrived into California from South Africa on 22 November.
President Joe Biden has also announced that the country’s transport mask mandate will be extended until 18 March 2022.
The measures requiring all passengers, unless medically exempt, to wear a mask on transport including trains, planes, buses, cruise ships and other forms of transportation, plus at public transport hubs, were originally due to expire on 18 January 2022.
But the latest coronavirus variant of concern, omicron, has seen countries around the world re-tighten domestic and travel restrictions.
The TSA first introduced the requirement to wear a mask on public transport in February 2021. The directive has since been extended several times, once from May to September, then from September to January.