With countries including the United States, India and France reporting their first Omicron cases, US Treasury Secretary Janet Yellen said she hoped the pandemic would not completely stifle economic activity.
"There's a lot of uncertainty, but it could cause significant problems. We're still evaluating that," she told the Reuters Next conference.
The new measures in Germany focus on the unvaccinated, who will only be allowed in essential businesses such as grocery stores and pharmacies, while legislation to make vaccination mandatory will be drafted for early next year.
"We have understood that the situation is very serious," Chancellor Angela Merkel told a news conference.
A nationwide vaccination mandate could take effect from February 2022 after it is debated in the Bundestag and after guidance from Germany's Ethics Council, she said.
Eager to avoid derailing a fragile recovery of Europe's biggest economy, Germany kept businesses open to the almost 69 percent of the population that is fully vaccinated as well as those with proof of having recovered from the virus.