The World Health Organization on Wednesday reported the highest single-day increase of coronavirus cases worldwide, warning the gradual end of lockdowns in wealthier countries may be obscuring an increasing crisis in the developing world.

Over the last 24 hours, 106,000 new cases of the virus were recorded, the body said, according to Reuters. Mike Ryan, head of the WHO’s emergencies program, said the world will “soon reach the tragic milestone of 5 million cases.”

“We still have a long way to go in this pandemic,” Director-General Tedros Adhanom Ghebreyesus told a news conference Wednesday. “We are very concerned about rising cases in low- and middle-income countries.”

The warning comes as the WHO has been at odds with the Trump administration, which has accused it of mishandling the pandemic and giving China preferential treatment. President Trump has vowed to permanently withhold funding from the WHO and withdraw the U.S. from the body.

Tedros said Wednesday that he has received a letter from Trump but offered no further details. He said he plans to conduct a review of the response to the pandemic. Member states voted in favor of a resolution calling for such a review earlier this week, according to Reuters.

“I said it time and time again that WHO calls for accountability more than anyone. It has to be done, and when it’s done it has to be a comprehensive one,” Tedros said Wednesday.

While Tedros offered no details on when the review would commence, Ryan said they typically began after an emergency concludes.

“I for one would prefer, right now, to get on with doing the job of an emergency response, of epidemic control, of developing and distributing vaccines, of improving our surveillance, of saving lives and distributing essential PPE [personal protective equipment] to workers and finding medical oxygen for people in fragile settings, reducing the impact of this disease on refugees and migrants,” he said, according to Reuters.