Spanish authorities are easing outdoor mask orders as COVID-19 infection numbers fall in the United States while South Korean curbs are extended for two weeks.

Spain will next week lift a requirement for people to wear masks outdoors as a measure against the coronavirus, extending a wider roll-back of restrictions as the contagion slowly recedes in the country.

The cabinet plans to approve an end to mandatory outdoor mask wearing at its weekly meeting on Tuesday and make it effective two days later, Health Minister Carolina Darias told La SER radio station on Friday.

Mask wearing outdoors was reinstated in late December to curb the spread of the emergent Omicron variant of the coronavirus.

"We said it would last only while it was strictly necessary," Darias said.

As contagion rates and other indicators have fallen for several days, the government considers the COVID-19 situation to have eased, she said.

Spain follows several other European countries that have begun to roll back COVID-related restrictions.

Outdoor masks are no longer compulsory in France and Italy announced on Wednesday it would release a timetable for a phase-out of restrictions.

Meanwhile, US authorities say new COVID-19 cases are falling in 49 of 50 states.

New cases per day have slumped by almost a half-million across the country since mid-January, the curve trending downward in every state except Maine.

The number of people in hospital with COVID-19 has fallen 15 per cent over that period to about 124,000.

Similarly, an early-warning program that looks for the virus in sewage found that COVID-19 infections are declining in the majority of participating US communities, according to data posted by the Centers for Disease Control and Prevention.

Deaths are still on the rise in at least 35 states, reflecting the lag time between when victims become infected and when they succumb.

But the trends are giving public health officials hope that the worst of Omicron is coming to an end although they caution that things could still go bad again and dangerous new variants could emerge.

Los Angeles County may end outdoor mask requirements in a few weeks, Public Health Director Barbara Ferrer said on Thursday.

But that is unlikely to happen before the February 13 Super Bowl, which will draw as many as 100,000 people to SoFi Stadium in Inglewood.

Overall, new cases in the US have plummeted from a record-obliterating average of more than 800,000 a day in mid-January to about 357,000.

But in South Korea, officials extended distancing rules on Friday for an additional two weeks as Omicron infections soar, including a 9pm curfew for restaurants and a six-person limit on private gatherings.

The restrictions were due to end on Sunday but Prime Minister Kim Boo-kyum said the extension was necessary to slow the spread of Omicron amid fears the Lunar New Year holiday, which ended on Wednesday, may have fuelled infections.

"Slowing the pace of the Omicron's spread, which is heading to its peak day after day, is a priority in this difficult circumstance," he said at a televised government response meeting.

New daily cases have tripled over the past two weeks but the number of deaths and serious infections have remained relatively low in the highly vaccinated country.