WASHINGTON — President Trump’s angry demands for punitive action against the World Health Organization were rebuffed on Tuesday by the organization’s other member nations, which decided instead to conduct an “impartial, independent” examination of the W.H.O.’s response to the coronavirus pandemic.

In a four-page letter late Monday, Mr. Trump had threatened to permanently cut off United States funding of the W.H.O. unless it committed to “major, substantive improvements” within 30 days. It was a major escalation of his repeated attempts to blame the W.H.O. and China for the spread of the virus and deflect responsibility for his handling of a worldwide public health crisis that has killed more than 90,000 people in the United States.

But representatives of the organization’s member nations rallied around the W.H.O. at its annual meeting in Geneva, largely ignoring Mr. Trump’s demand for an overhaul and calling for a global show of support in the face of a deadly pandemic.

The outcome left the United States isolated as officials from China, Russia and the European Union chided Mr. Trump over his heated threats even as they acknowledged the need for a review of how the W.H.O. performed as the virus spread from China to the rest of the world.

Public health experts noted that Mr. Trump’s threats to withdraw from the organization and halt funding ignored the reality that any such moves would require the consent of Congress, something many analysts said was unlikely.

But the president’s continued attacks on the W.H.O., experts said, threatened to hobble the organization at a critical moment and seriously damage international efforts to combat the virus, especially in poorer countries that depend heavily on the agency.

“Just when the world was trying to come together over an unprecedented health crisis, it’s all splintered apart,” said Lawrence O. Gostin, the director of the O’Neill Institute for National and Global Health Law at Georgetown University. “This kind of disruption and setting global health on fire by the Trump administration is going to cost lives.”

Virginie Battu-Henriksson, a spokeswoman for the European Commission, said it was “the time for solidarity, not the time for finger pointing.” Valentina I. Matviyenko, the speaker of the upper house of the Russian Parliament, said Moscow would stand behind the W.H.O., adding that there was “certainly no reason to perform a mock trial or any kinds of investigations” or to “destroy the useful things that have been accumulated for decades by mankind.”

The resolution approved by W.H.O. members without objection promised a “comprehensive evaluation” of the organization that would review “experience gained and lessons learned from the W.H.O.-coordinated international health response to Covid-19.”

In a statement, the White House sought to claim victory, suggesting that the resolution amounted to a mandate to investigate Mr. Trump’s concerns about the origins of the virus.

But the document, which was sponsored by scores of American allies but not the United States, fell far short of the condemnation of the W.H.O. that Mr. Trump issued in his letter Monday night. Officials at the White House and the Department of Health and Human Services did not respond to emails seeking comment.

Mr. Trump has railed against the W.H.O. for weeks as his own political and public health crisis at home has intensified, saying the organization is in the thrall of China, where the virus originated. In his letter Monday night, he said the W.H.O. was responsible for many deaths because it failed to challenge the version of events provided by Xi Jinping, the president of China, regarding the origin of the virus and its initial spread.

“As the source of the outbreak, China has a special responsibility to pay more and to give more,” John Ullyot, a spokesman for Mr. Trump’s National Security Council, said in a statement before the meeting.

The president accuses the global health group of failing to act quickly and aggressively enough against the virus, in effect denouncing the organization for the very missteps and failures that have been leveled at him and his administration. Public health experts have said the president’s public denials of the virus’s dangers slowed the American response, which included delayed testing and a failure to stockpile protective gear.

Foreign policy experts said Mr. Trump’s attacks on the W.H.O. provided a strategic opening for China, which announced on Monday that it would spend $ 2 billion in the global fight against the pandemic, and served mainly to undercut the interests of the United States by angering its closest allies.

“We’ve been actively alienating them, which is not a good competitive strategy on our part,” said Thomas J. Christensen, the director of the China and the World program at Columbia University and a former U.S. deputy assistant secretary of state for East Asian and Pacific Affairs. “We’re weakening our own diplomatic profile around the world, and strengthening China’s.”

Mr. Trump’s criticism about the W.H.O.’s coziness with China was particularly ironic given his praise for the country early in the pandemic, when he was trying to complete negotiations on a trade deal.

Besides his accusations, Mr. Trump’s letter also contained a number of falsehoods and misleading statements. One of them was that the W.H.O. “consistently ignored credible reports of the virus spreading in Wuhan in early December 2019 or even earlier, including reports from the Lancet medical journal.”

But in a statement Tuesday morning, The Lancet pointed out that the journal “published no report in December 2019 referring to a virus or outbreak in Wuhan or anywhere else in China.” The journal said its first reports about the virus were published on Jan. 24, just six days before the W.H.O. declared an international emergency.

Mr. Trump’s attacks on the W.H.O. are at the center of the president’s appeal to his core supporters — a message that his political advisers intend to highlight as Mr. Trump fights for a second term this November. To many of the president’s supporters, the W.H.O. and other international organizations are to blame for lost jobs, low wages and economic uncertainty.

And as Mr. Trump seeks re-election, he will need to convince a broad part of the electorate that he is not responsible for the tens of thousands of deaths and economic calamity caused by the virus. Creating enemies out of the W.H.O. and the Chinese government could be an effective way of blunting what is sure to be fierce criticism from Democrats this fall about his handling of the pandemic.

The W.H.O. resolution approved on Tuesday did not provide specific direction to investigate one of Mr. Trump’s central allegations against the global health group: that it was too credulous in believing China’s assertions about the virus and its leaders’ denials that it was not created in a Chinese lab.

Scientists who have studied the genetics of the virus say that the overwhelming probability is that it leapt from animal to human in a non-laboratory setting, as was the case with H.I.V., Ebola and SARS.

China did not object to the resolution, but Mr. Xi said on Monday that any such inquiry should wait until the health crisis is brought under control.

At the White House on Tuesday, Mr. Trump said the W.H.O. would “have to clean up their act.”

“They have to do a better job,” he said. “They have to be much more fair to other countries, including the United States, or we’re not going to be involved with them and we’ll do it in a separate way.”

In a closing statement on Tuesday that marked the end of the two-day assembly, Tedros Adhanom Ghebreyesus, the director general of the W.H.O., reiterated his support for an investigation into the organization’s handling of its response to the virus and highlighted the need for cooperation.

“Covid-19 has robbed us of people we love. It has robbed us of lives and livelihoods. It has shaken the foundations of our world,” he said. “It threatens to tear at the fabric of international cooperation. But it has also reminded us that for all our differences, we are one human race, and we are stronger together.”

Michael D. Shear reported from Washington, and Andrew Jacobs from New York.