The US is weighing the tightening of testing requirements for international arrivals amid concern over the emergence of the Omicron variant.
Enhanced measures include a requirement for a pre-departure test on the day before travel for all travellers, rather than just those who are not fully vaccinated.
Current rules required double-jabbed travellers to take a test within three days of departure.
The US Centers for Disease Control and Prevention said in a statement: “CDC is working to modify the current Global Testing Order for travel as we learn more about the Omicron variant; a revised order would shorten the timeline for required testing for all international air travellers to one day before departure to the United States.”
The Associated Press reported that other measures being considered included the extension of post-arrival testing requirements and possible quarantine for arrivals.
In the UK, travel restrictions have been tightened to include a requirement for a negative PCR test taken within two days of arrival, with passengers expected to self-isolate until results are returned.
US president Joe Biden said in a news conference on Monday that the extent of the spread of the Omicron variant would dictate whether further restrictions would be necessary.