The Biden administration is lifting its requirement that international air travellers to the US take a Covid-19 test within a day before boarding their flights, easing one of the last remaining government mandates meant to contain the spread of the coronavirus.

A senior administration official said the mandate expires Sunday at 12:01am EDT, saying the Centers for Disease Control and Prevention has determined that it's no longer necessary. The official, speaking Friday on the condition of anonymity to preview the formal announcement, said that the agency would reevaluate the need for the testing requirement every 90 days and that it could be reinstated if a troubling new variant emerges.

The Biden administration put in place the testing requirement last year, as it moved away from restrictions that banned nonessential travel from several dozen countries — most of Europe, China, Brazil, South Africa, India and Iran — and instead focuses on classifying individuals by the risk they pose to others. It came in conjunction with a requirement that foreign, non-immigrant adults traveling to the United States need to be fully vaccinated, with only limited exceptions.

The initial mandate allowed those who were fully vaccinated to show proof of a negative test within three days of travel, while unvaccinated people had to present a test taken within one day of travel.

In November, as the highly transmissible omicron variant swept the world, the Biden administration toughened the requirement and required all travellers, regardless of vaccination status, to test within a day of travel to the US.

Airline and tourism groups have been pressing the administration for months to eliminate the testing requirement, saying it is discouraging people from booking international trips. Many other countries have lifted their testing requirements for fully vaccinated and boosted travellers in a bit to increase tourism.

In February, the groups argued the testing requirement was obsolete because of the high number of omicron cases already in every state, higher vaccinations rates and new treatments for the virus.

"I'm glad CDC suspended the burdensome coronavirus testing requirement for international travellers, and I'll continue to do all I can to support the strong recovery of our hospitality industry," Sen. Catherine Cortez Masto, D-Nev., said in a statement.

The lifting of the requirement comes six weeks after a federal judge ended the CDC's mask requirement for mass transit, including trains, planes, buses and transit hubs, saying the agency exceeded its authority. The Biden administration is appealing that ruling, saying it aims to protect the CDC's ability to respond to future health emergencies.

The official said the CDC will continue to recommend Covid-19 testing prior to air travel of any kind as a safety precaution.