President Donald Trump on Monday threatened to make the freeze on U.S. funding for the World Health Organization permanent.
He also laid out allegations of "missteps" in the way the agency responded to the coronavirus in a letter he said he sent to the WHO's leader.
The letter, which was posted to Trump's Twitter account and comes midway through the World Health Assembly, is addressed to WHO Director-General Tedros Adhanom Ghebreyesus. It accuses the organization of an "alarming lack of independence from the People's Republic of China."
The coronavirus outbreak began in Wuhan, China. As of late Monday, it had killed more than 318,000 people around the world, according to Johns Hopkins University. In the U.S., more than 91,100 have died, according to an NBC News count.
"It is clear the repeated missteps by you and your organization in responding to the pandemic have been extremely costly for the world," the letter says. "The only way forward for the World Health Organization is if it can actually demonstrate independence from China."
The WHO has no authority to force foreign governments to divulge medical information or open doors to its hospitals and labs, experts have said.
Trump last month announced that the U.S. was halting funding for the WHO pending a review of its response to the initial coronavirus outbreak.
The president said the U.S. sends $500 million a year to the organization. The U.S. is the largest WHO contributor out of 196 countries, accounting for roughly 15 percent of the agency's budget.
Trump's letter states that his administration has been in discussions with the organization, "but action is needed quickly." It says a review confirmed many of the issues Trump previously raised.
"[I]f the World Health Organization does not commit to major substantive improvements within the next 30 days, I will make my temporary freeze of United States funding to the World Health Organization permanent and reconsider our membership in the organization," the letter reads.
The move to cut WHO funding has been criticized.
Dr. Patrice Harris, president of the American Medical Association, has said: "Cutting funding to the WHO — rather than focusing on solutions — is a dangerous move at a precarious moment for the world."
U.N. Secretary-General António Guterres said in April that there will be a time to review actions and learn lessons but that the time is not during a crisis.
"It is also not the time to reduce the resources for the operations of the World Health Organization or any other humanitarian organization in the fight against the virus," the secretary-general said in the statement.
China has vehemently denied that it concealed details about the outbreak, and the WHO has strongly defended its response, saying it took urgent action at the first signs of the epidemic in Wuhan.
At the 73rd World Health Assembly, at least 116 countries backed a draft resolution that is set to call for "an impartial, independent and comprehensive" evaluation of the WHO during the pandemic. It also seeks to identify the origin of the virus.
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Tedros, the WHO director-general, welcomed the resolution calling for an inquiry and said an "impartial, independent and comprehensive evaluation" would happen "at the earliest appropriate moment."
Guterres called for unity among nations fighting the pandemic. "Either we stand together or we fall apart," he said.