President Joe Biden has unveiled stricter Covid-19 travel rules as the US confirmed a handful of cases of the Omicron variant from coast to coast.

From next week, international travellers to the US, including Americans, must get a Covid test 24 hours before they depart, regardless of vaccination status.

Mask requirements on planes, trains and buses will be extended until mid-March.

Millions of free and insurer-funded home tests will also be made available.

Ten cases of the Omicron variant have been detected in the US: in California, Colorado, Minnesota, and New York, and in Hawaii, where authorities say that person had no recent travel history.

State health officials have reported only mild symptoms in these cases.

The variant has now been found in up to 30 countries, according to reports.

It is still not clear whether Omicron, a highly mutated variant, is associated with more transmission or more risk of evading vaccines.