Director General Dr Tedros Adhanom Ghebreyesus said, "too many countries [were] headed in the wrong direction".
Cases were rising where proven measures were not adopted or followed, he added.
The Americas are the current epicentre of the pandemic. The US has seen a rise in cases amid tensions between health experts and President Donald Trump.
The US, the worst affected country, has over 3.3 million confirmed cases and more than 135,000 deaths, according to Johns Hopkins University.
What has the WHO said?