On Thursday (2 December), the White House confirmed it would reduce its pre-departure testing window from 72 hours to 24 hours, with the change set to come into effect "early next week".

In effect, it means all visitors to the US – vaccinated and unvaccinated – will have to test negative for Covid-19 at most a day before their travel.

Additionally, the administration has extended its requirement for travellers to wear masks on aircraft, trains and other forms of public transport through to mid-March 2022.

In a statement confirming the changes, the White House added president Joe Biden would announce additional, albeit yet-unspecified, steps to "strengthen the safety of international travel".

"Early next week, the United States will tighten pre-departure testing protocols by requiring all inbound international travellers to test within one day of departure globally, regardless of nationality or vaccination status," said the White House.

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

On masks, it added: "The administration will continue to require masking during international or other public travel – as well as in transportation hubs such as airports or indoor bus terminals – through [to] 18 March as we continue to battle Covid-19 this winter."

The minimum fine for non-compliance with the mask order will be doubled to $500 with fines ranging up to $3,000 for repeat offenders.