It is dangerous to assume omicron will be the last variant to emerge and that the world is in the "end game" in the battle against COVID-19, the head of the World Health Organization (WHO) said Monday as he urged countries to work together to bring an end to the acute phase of the pandemic now that they have all the tools to do so.

However, Tedros Adhanom Ghebreyesus said it was possible this year to exit the acute phase of the pandemic where COVID-19 constitutes a global health emergency if strategies and tools such as testing and vaccines are used in a comprehensive way.

Speaking at the opening of the WHO's Executive Board meeting, Tedros said since omicron was first identified a little over nine weeks ago, more than 80 million cases had been reported to the U.N. agency, more than the number reported in the whole of 2020.

"Conditions are ideal for more variants to emerge," he added.

"The COVID-19 pandemic is now entering its third year and we are at a critical juncture," said Tedros at a press conference alongside Svenja Schulze, Germany's development minister.

"We must work together to bring the acute phase of this pandemic to an end. We cannot let it continue to drag on, lurching between panic and neglect."

Tedros said on Monday that Germany had become the agency's largest donor, without giving details. Historically, the United States has made the biggest financial contribution among member states to the organization.

Schulze said that the top priority of Germany, which took over the G-7 presidency, is to end the pandemic worldwide and called for a "massively accelerated, truly global vaccination campaign" in order to do so.

The event in Geneva kicks off a week of WHO Executive Board meetings where key aspects of the U.N. health agency's future are due to be discussed, including Tedros' bid for a second term and a proposal to make the agency more financially independent.