The WHO chief took on so-called "vaccine diplomacy" on Monday, slamming countries for using COVID-19 jabs to gain competitive advantage rather than engaging in true cooperation to end the pandemic.
"Vaccine diplomacy is not cooperation," Tedros Adhanom Ghebreyesus told reporters from the World Health Organization's headquarters in Geneva.
The UN health agency chief's was responding to a question about allegations that countries such as Russia and China, which have donated large quantities of their home-grown COVID vaccines to nations desperate for the jabs, were doing so in exchange for market access and influence.
Tedros decried "geopolitical maneuvering" at a time when only "clear and clean cooperation... can help".
"We cannot defeat this pandemic through competition," he said.
"If you compete for resources, or if you compete for geopolitical advantages, then the virus gets advantage."
The pandemic has killed close to 3.3 million people since the new coronavirus first emerged in late 2019, upending normal life and causing global economic havoc.
Tedros said the world was now seeing the number of new Covid cases leveling off, but stressed "it is an unacceptably high plateau".
He pointed out that there were more than 5.4 million new cases and nearly 90,000 deaths reported globally last week alone, with numbers still soaring in India especially.
And while rapid vaccination programs have allowed a number of wealthy nations to start taking steps towards normality, the virus is still surging in many countries and concerns are growing about global vaccine inequality.
Tedros noted "low- and lower-middle-income countries account for 47 percent of the world's population, but have received just 17 percent of the world's vaccines."
"Redressing this global imbalance is an essential part of the solution," he said.
But he insisted that even countries with broad vaccine access and seemingly declining outbreaks needed to remain vigilant.
"We have been here before. Over the past year, many countries have experienced a declining trend in cases and deaths, have relaxed public health and social measures too quickly, and individuals have let down their guard, only for those hard-won gains to be lost," he said.