President Donald Trump on Monday told the World Health Organization, a body that he has accused of being "China-centric," that he will permanently freeze U.S. funding of it and reconsider membership unless it commits to major reform within the next 30 days.

The warning came after the Trump administration placed a hold on all funding to the WHO in April, pending an investigation of what it sees as the organization's failed response to the coronavirus pandemic that has killed more than 318,000 worldwide.

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In a letter addressed to WHO Director General Tedros Ghebreyesus, posted on Trump's Twitter account, the president said the review has underscored concerns and other issues that should be addressed, especially the agency's "alarming lack of independence" from China.

The four-page letter contained a list of alleged missteps taken by the WHO, including ignoring credible reports of the virus spreading in China's central city of Wuhan in early December or even earlier, and reaffirming in January a claim China made at the time that the virus could not be transmitted between humans.

"It is clear the repeated missteps by you, and your organization in responding to the pandemic have been extremely costly for the world. The only way forward for the World Health Organization is if it can actually demonstrate independence from China," Trump said in the letter.

"If 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," he added.

Permanently cutting off U.S. funding would deal a heavy blow to the WHO. The United States was the top contributor in 2018 and 2019, providing $893 million in total, accounting for about 15 percent of the Geneva-based agency's funding.

Speaking to reporters on Monday, Trump reiterated his frustration that the United States has not been treated properly, given that it is providing between $400 million and $500 million per year to the WHO while China contributes $40 million a year or less.

Trump, who has faced criticism for his handling of the pandemic ahead of the November election, has increasingly shifted the blame to the WHO and China, where the virus was first detected late last year.

The letter to the WHO also included criticism against Beijing for not having shared important information in a timely fashion and lacking transparency.

"And, to this day, China continues to deny international access to their scientists and relevant facilities, all while casting blame widely and recklessly and censoring its own experts," the letter said.

Earlier Monday, U.S. Secretary of Health and Human Services Alex Azar called for the need to reform the WHO during a virtual meeting of the World Health Assembly, the WHO's decision-making body.

"The status quo is intolerable. WHO must change, and it must become far more transparent and far more accountable," he said.

The secretary also said, "at least one member state made a mockery of their transparency obligations" in an apparent attempt to conceal the outbreak. However, he did not explicitly name China.

The secretary, meanwhile, emphasized that it is "critical" that Taiwan, which is seen as having succeeded in containing the virus, participate as an observer at the assembly to "bring the helpful perspective regarding their effective and exemplary response."

U.S. Secretary of State Mike Pompeo was even harsher in criticizing Taiwan's exclusion from the assembly meeting, saying in a statement that the WHO chief chose "not to invite Taiwan under pressure" from China despite having the "power and precedent" to include Taiwan in the assembly's proceedings.

Pompeo said the absence of Taiwan deprives the assembly of the island's scientific expertise on the disease, and "further damages the WHO's credibility and effectiveness at a time when the world needs it the most."

Taiwan, officially known as the Republic of China, was expelled from the WHO in 1972 after its seat at the United Nations was taken over by the People's Republic of China a year before.