The World Health Organization is calling on rich countries to delay till the end of September plans to give out booster shots of COVID-19 vaccines to their largely protected populations in a gesture that would allow at least 10 percent of people in every country to be vaccinated.

But the appeal, made by WHO Director-general Tedros Adhanom Ghebreyesus on Wednesday, fell on deaf ears in the United States, which was among the first nations to begin vaccinations late last year. Tedros, who has long pushed for vaccine equity, was speaking on the day that infections surpassed 200 million worldwide, according to data from Johns Hopkins University.

Tedros said more than 4 billion vaccine doses have been administered globally, with more than 80 percent going to high- and upper-middle income countries. That's despite the fact that these countries account for less than half the world's population.

"While hundreds of millions of people are still waiting for their first dose, some rich countries are moving toward booster doses," he said in a media briefing.

However, Washington was swift in shooting down the proposal.

"We definitely feel that it's a false choice and we can do both," White House press secretary Jen Psaki told reporters.

"Also in this country (we) have enough supply to ensure that every American has access to a vaccine."

The US in July signed a deal with Pfizer and BioNTech to buy 200 million additional doses of the companies' vaccine to help with pediatric vaccination as well as possible booster shots.

On Thursday, French President Emmanuel Macron said on his Instagram account that it was likely that the elderly and vulnerable would need a third vaccine shot.

WHO officials say the science is unproven about whether giving booster shots to people who have already received two vaccine doses is effective in preventing the spread of the coronavirus.

Although the WHO chief said he understands that all governments want to protect their people from the Delta variant, Tedros criticized countries that have already used most of the global supply of vaccines and are now using even more of it as "the world's most vulnerable people remain unprotected".

Urgent reversal

He stressed the need for an urgent reversal in the flow of vaccines to ensure that most supplies went to poorer countries.

"WHO is calling for a moratorium on boosters until at least the end of September, to enable at least 10 percent of the population of every country to be vaccinated,"Tedros said.

"To make that happen, we need everyone's cooperation, especially the handful of countries and companies that control the global supply of vaccines."

He called on the G20 countries to make concrete commitments to support the WHO's global vaccination targets when health ministers from the G20 group of nations meet in a month.

Tedros also asked for producers to prioritize COVAX, a worldwide initiative aimed at equitable access to COVID-19 vaccines, as well as for influential figures as athletes, investors and faith leaders to support the WHO's call for a pause in plans for booster shots.

"At the same time, we must all remember that vaccines are not the only tool. Indeed, there is no single tool that will defeat this pandemic," Tedros said. "We can only defeat it with a comprehensive approach of vaccines in combination with the proven public health and social measures that we know work."

By midafternoon on Wednesday in the US, the Johns Hopkins University had tallied 200,014,602 coronavirus infections worldwide, with 4,252,873 deaths.

The data showed the US with 35,292,721 cases and 614,666 deaths, both the highest counts around the world, accounting for nearly 18 percent of the cases and almost 15 percent of the deaths.

India has recorded the world's second-largest caseload, followed by Brazil. The global caseload reached the grim milestone of 100 million on Jan 26, and doubled in more than half a year.

As the most effective tool in the fight against COVID-19, at least 4.27 billion doses have been administered globally so far, according to a count from Agence France-Presse.

Bo Leung in London, Xinhua and agencies contributed to this story.