Chinese President Xi Jinping said on Monday that Beijing had been "transparent" throughout the coronavirus crisis, and offered to share a vaccine as soon as one was available – as well as $2 billion in aid.
Governments in the US, Australia and Europe have called in recent weeks for an investigation into the origins of the virus, which has become a flashpoint in deteriorating tensions between Washington and Beijing.
Both US President Donald Trump and Secretary of State Mike Pompeo have accused China of a lack of transparency over the issue, and repeatedly pushed the theory that the virus leaked from a Chinese maximum-security laboratory.
Addressing the first-ever virtual gathering of the WHO's annual assembly, Xi claimed China has "always had an open, transparent and responsible attitude," and had shared information on the virus in a timely manner.
Chinese scientists have said that the virus emerged from a market that sold wild animals in the central Chinese city of Wuhan in December, though officials have more recently cast doubt about its origins.
Authorities in Wuhan have come under fire for reprimanding and silencing doctors who raised the alarm about the virus late last year. China is also accused of having delayed confirmation that the virus was transmissible between humans.
China has strenuously denied accusations of a cover up, insisting it has always shared information with the World Health Organization (WHO) and other countries in a timely manner.
The assembly was set to discuss a resolution tabled by the European Union that calls for an "impartial, independent and comprehensive evaluation" of the global response to the coronavirus crisis.
Speaking via videolink with a painting of the Great Wall in the background, Xi said China supports a "comprehensive evaluation" of the global response to the pandemic after it "has been brought under control" and that the probe should be led by the WHO.
The inquiry should "sum up experiences and improve shortcomings" and "adhere to the principles of objectivity and fairness", Xi told the World Health Assembly.
WHO chief Tedros Adhanom Ghebreyesus pledged at the assembly to launch an independent probe to review the coronavirus pandemic response "at the earliest appropriate moment".
Making vaccine 'global public good'
While Washington has tried to pin the blame for the pandemic on China, Beijing has sought to reframe the narrative, offering medical aid to countries around the world.
With the world racing to find a drug to stop the pandemic, Xi pledged on Monday to make any potential vaccine developed by China a "global public good" once it was put into use.
This move would be China's contribution to achieving accessibility and affordability of a vaccine in developing countries as well, Xi said.
China says it has five potential vaccines in clinical trials. A top Chinese health official said last week that more vaccine candidates are in the pipeline and awaiting approval for human trials.
Experts say it will take at least 12 to 18 months to develop an effective vaccine, or even longer.
Xi also told the assembly that China will provide $2 billion in international aid over two years to help with Covid-19 response and economic development in affected countries, especially in the developing world.
"China will work with members of the Group of 20 nations to implement the debt relief initiative for the poorest countries," he said.
Xi also said China would work with the UN to set up a "global humanitarian response depot" in China and facilitate the international movement of medical supplies.
Trump threatens freeze on WHO funding
While the WHO said it would launch an independent review of its response to the pandemic, US President Donald Trump renewed his attack on the global body, branding it a "puppet of China" and threatening a permanent freeze on US funding.
A wide range of country leaders and health ministers hailed the WHO's efforts but US health secretary Alex Azar said its "failure" to obtain and provide vital information on Covid-19 had cost lives.
Washington has suspended its funding to the health body, accusing it of being too close to Beijing, and covering up and mismanaging the pandemic.
"In an apparent attempt to conceal this outbreak, at least one member state made a mockery of their transparency obligations, with tremendous costs for the entire world," said Azar, pointing the finger at Beijing.
Later on Monday, Trump threatened to permanently freeze US funding to the WHO and reconsider its membership unless "substantive improvements" were made within the next 30 days.
"The only way forward for the World Health Organization is if it can actually demonstrate independence from China," Trump said in a letter to the WHO chief.
"They're a puppet of China, they're China-centric to put it nicer," he said earlier at the White House. "They gave us a lot of bad advice."
Trump has accused the WHO of blindly taking the word of China, where the SARS-CoV-2 virus was first detected.
Critics say Trump, who had earlier praised China's response, is trying to divert attention from his handling of the pandemic in the United States, which has suffered by far the highest death toll.
The annual World Health Assembly (WHA) has this year been trimmed from the usual three weeks to just two days, and is focusing solely on the pandemic.
UN Secretary-General Antonio Guterres told the assembly the Covid-19 crisis was a "wake-up call".
"Deadly global threats require a new unity and solidarity," he said. "We have seen some solidarity, but very little unity... Different countries have followed different, sometimes contradictory, strategies and we are all paying a heavy price."
The UN head said many countries had ignored the WHO's recommendations.
"As a result, the virus has spread across the world and is now moving into the global South, where its impact may be even more devastating, and we are risking further spikes and waves," Guterres said.
Protecting developing countries was not a matter of charity but of enlightened self-interest, he said. "We are as strong as the weakest health systems," he warned.
Guterres called for an immediate focus on unity to get through the present emergency. "Either we get through this pandemic together, or we fail. Either we stand together, or we fall apart."
French President Emmanuel Macron and German Chancellor Angela Merkel insisted that any vaccine must be available to everyone.