(Adds Moon quote, political background)

SEOUL, Feb 18 (Reuters) - South Korea's new daily COVID-19 cases topped 100,000 for the first time amid its Omicron outbreak, with authorities saying social distancing measures would be only slightly eased ahead of the March 9 presidential election.

Authorities announced on Friday they would move a curfew on restaurants and cafes from 9 p.m. to 10 p.m., a nod to increasing criticism from business owners.

"The situation for small business owners and the self-employed is desperate," President Moon Jae-in told a meeting of aides on Friday, when calling for the parliament to quickly pass a supplemental budget with measures for "resolving the difficulties of the people's livelihood."

Other anti-pandemic rules such as a six-person cap on private gatherings, a seven-day quarantine for international arrivals, mask mandates in public spaces, and vaccine passes for a range of businesses, will be in place until at least March 13, officials said, after the election.

Moon is barred by the constitution from running again. The two leading contenders are locked in what may be the tightest race in 20 years.

As cases have surged, South Korea has scaled back the tracking, tracing, and quarantining strategy that helped it keep earlier waves in check.

Now people with few or no symptoms are being treated at home rather than health facilities, and only people in priority groups get immediate access to free PCR tests.

Others must first take a rapid antigen test for faster initial diagnosis.

Some experts warn daily cases could still double or triple and have called for maintaining social distancing measures. Authorities say so far serious cases have remained manageable, and deaths are relatively low.

More than 58% of the country's 52 million population has received vaccine booster shots. Overall, more than 44 million people, accounting for 86.2% of the population, are fully vaccinated.

The KDCA said 109,831 new COVID-19 cases had been reported as of midnight on Thursday, bringing the country's total to 1,755,809. An additional 45 deaths were reported, for a total of 7,283. (Reporting by Josh Smith Editing by Shri Navaratnam and Lincoln Feast.)