GENEVA: Facing the most disruptive pandemic in generations, the technocratic halls of the World Health Organization are now the scene of pitched battles in an increasingly bitter proxy war between the China and the United States.

At the UN health agency's annual assembly this week, Chinese President Xi Jinping joined by video conference to offer more money and support. Meanwhile, U.S. President Donald Trump railed against the WHO in a letter accusing it of covering up the coronavirus outbreak with China — and threatening to permanently halt U.S. funding that has been its main financial lifeblood for years.

It marked the latest showdown between the world's last superpower and the rising Asian giant vying to supplant it on the global stage — this time against the backdrop of a disease that has killed over 300,000 people, left hundreds of millions jobless and ground the world economy to a halt.

For America’s allies in the West and beyond — who have counted on the postwar stability and prosperity that the United States has fostered — the standoff was another gut-check moment about the “America First” leader, now heading into a tough reelection contest.

Lawrence Gostin, director of the WHO Collaborating Center on Health and Human Rights at Georgetown University, said the withdrawal of the U.S. from the global health world would mark a seismic political shift.

“What the U.S. is doing is acting like a bully, making an existential threat to the WHO, and my worry is if the U.S. ever made good on that pledge, the world would splinter,” he said. “This is giving an enormous political prize to China because China has long been looking for a chance to shine on the global stage."

A U.S. exit would likely weaken the global health agency and leave the U.S. and China to each fund their own projects, Gostin said.

At the assembly that ended Tuesday, European Union leaders tried to strike a middle ground between the two rivals, and the agency’s director-general simply tried to keep the focus on fighting the disease — not each other.

The assembly’s opening day Monday was book-ended by two very different messages. On one side, Xi, serene beside the Chinese flag and a landscape mural, called in to say that China would offer $2 billion over two years to help with the COVID-19 response and economic fallout. He vowed that any vaccine against the disease developed in his country would be made a “global public good.”

On the other, Trump threatened to cut U.S. funding to the WHO for good unless the agency commits to “substantive improvements” in the next 30 days, in a letter to agency Director-General Tedros Adhanom Ghebreyesus. It's not clear what those improvements are.

“I cannot allow American taxpayer dollars to continue to finance an organization that, in its present state, is so clearly not serving America’s interests,” Trump wrote.

The U.S. is the biggest WHO donor, providing about $450 million a year.

Europeans looked on aghast.

“Watching the World Health Assembly today was observing the post-American world,” tweeted former Swedish Prime Minister Carl Bildt, co-chair of the European Council on Foreign Relations. “A confident and assertive China with clear strategic approach. A EU trying to rescue what’s left of global cooperation. And a disruptive U.S. more keen on fighting China than fighting COVID19."

Trump’s threat followed an intense internal debate within the administration between aides intent on eliminating all funding for the WHO and those favoring a more measured response, such as pegging U.S. funding temporarily to the level provided by China, according to three U.S. officials familiar with the matter. The officials spoke on condition of anonymity because they were not authorized to discuss the issue publicly.

The WHO and other institutions have often drawn criticism from conservatives who are part of Trump's base and disdain U.N.-style internationalism.

In the end, Trump reiterated a number of accusations and complaints that he has publicly made before, such as that the agency’s claims about the virus were “either grossly inaccurate or misleading.”

He also alleged that the WHO had “consistently ignored credible reports of the virus spreading in Wuhan in early December 2019 or even earlier, including reports from the Lancet medical journal.”

On Tuesday, the Lancet called that characterization “factually incorrect,” noting that the first papers published on the coronavirus did not appear until January.

George Davey Smith, an epidemiologist at the University of Bristol, called Trump's letter “an undisguised political attack on China.”

WHO acknowledged receipt of the missive and said it was considering it.

Tedros, an Ethiopian who goes by his first name, appeared determined to rise above the new bout of criticism, saying “WHO’s focus now is fighting the pandemic with every tool at our disposal.”

Medical experts said the attacks from Trump, who has repeatedly shunned and berated international institutions, were hurting the WHO's ability to protect global health.

Devi Sridhar, a professor of global health at the University of Edinburgh, said the letter was likely written for Trump’s political base and meant to deflect blame for the virus’ devastating impact in the U.S., which has by far the most infections and deaths in the world.

“China and the U.S. are fighting it out like divorced parents while WHO is the child caught in the middle,” she said.

Nonetheless, the assembly produced a unanimous resolution — with both China and the U.S. on board — that backs global cooperation to find tools to address COVID-19 and evaluate the world’s response, as coordinated by WHO, to it.

It wasn’t immediately clear how, when or by whom that evaluation will be conducted. Xi expressed support for a review — but said it should wait until after the pandemic is over.

The European Union, the resolution's chief architect, urged countries to support the WHO in the wake of Trump’s attacks.

“This is the time for all humanity to rally around a common cause,” European Commission President Ursula von der Leyen said.