The US and Australia became the latest countries to establish locally transmitted cases of the variant, as Omicron infections pushed South Africa's total cases past three million.
And India affirmed its third Omicron infection today, with cases also now spotted in Sri Lanka, South Korea, and Malaysia.
The WHO suggested it could take weeks to decide how dangerous the variant is, whether it makes more severe illness, and how effective treatments and vaccines are against it.
"We're going to get the answers that everybody out there needs," WHO emergencies director Michael Ryan said.
The WHO said yesterday it had still not detected any news of deaths related to Omicron, but the new variant's spread has led to warnings that it could cause more than half of Europe's Covid cases in the next few months.
The new variant could also reduce global economic healing, just as the Delta variant did, International Monetary Fund chief Kristalina Georgieva said on Friday.
"Even before the arrival of this new variant, we were concerned that the recovery, while it continues, is losing some momentum," she said.
"A new variant that may spread very rapidly can dent confidence."
Health Secretary Sajid Javid today met with the World Health Organisation's director-general Tedros Adhanom Ghebreyesus, portraying it as "productive".
He tweeted: "Productive meeting with @DrTedros and his team to share our findings so far on Omicron.
"We continue to work with @WHO on our global treaty to prepare for and respond to future pandemics, and on building a global surveillance network."
Six more US states approved infections of the variant yesterday but the Delta strain likely stays a greater threat as winter sets in and Americans gather for the holidays, experts said.
New Jersey, Maryland, Missouri, Nebraska, Pennsylvania, and Utah each reported their first cases of the Omicron variant on Friday.
Missouri was expecting CDC approval of a case involving a St. Louis resident who had recently traveled within the United States.
And the mutant spread in Australia today, challenging plans to revive the economy as a cluster in Sydney grew to 13 cases and an infection was suspected in the state of Queensland.
Federal officials are staying with a project to re-establish the economy on the hope that the new variant shows to be easier than previous strains, but some state and territory governments have moved to toughen their domestic border controls.
Australia reported its first community transmission of Omicron on Friday at a school in Sydney. Authorities are examining the cause.