Argentina’s chainsaw-wielding president, Javier Milei, met the American health and human services secretary, Robert F. Kennedy Jr., on Tuesday as the country ratified its decision to follow the United States and withdraw from the World Health Organization.

Mr. Milei, a right-wing economist, has promised a dramatic shake-up of his nation’s institutions. He has drawn comparisons to President Trump for his populist stances.

Mr. Kennedy posted a photo of him holding a gold chainsaw with Mr. Milei and said they were working together on the creation of an alternative international health system “based on gold-standard science.”

The Argentinian health minister, Mario Lugones, issued a joint statement with Mr. Kennedy citing the WHO’s handling of the Covid pandemic and “serious structural and operational shortcomings” that undermined global trust.

“There are well-documented concerns regarding the early management of the pandemic and the risks associated with certain types of research,” the statement read. “Rather than ensuring timely transparency, the WHO failed to provide critical access to information, impairing countries’ ability to act swiftly and effectively, with devastating global consequences.”

The United States said it decided to withdraw from the WHO because the organization never put in place meaningful reforms and demanded America cover too big a portion of its operating funds. The WHO is also accused of becoming increasingly politicized. “The organization has shifted away from its founding mission, becoming increasingly reliant on voluntary contributions and vulnerable to the influence of non-scientific agendas,” the joint statement read.

Mr. Kennedy says America will work with Argentina toward building a modern global health cooperation model “grounded in scientific integrity, transparency, sovereignty, and accountability.”

“We can no longer support a system that fails to protect our people or deliver on its mandate,” the statement concludes. “The United States and Argentina invite all nations committed to scientific integrity, transparency, and the defense of human dignity to join us in shaping a new era of global health cooperation — one focused on results, sovereignty, and a safer future for all.”

Last week, Mr. Kennedy called for other countries to withdraw from the WHO. Speaking to the World Health Assembly in Geneva last week, he suggested health ministers around the world should join in a “new era of cooperation.”