Going forward, the United States will work with — not against — the World Health Organization. That was the message delivered Thursday by President Biden’s chief medical adviser and Vice President Harris.

In remarks to the U.N. health agency’s executive board Wednesday morning, Anthony S. Fauci confirmed that the United States will halt its withdrawal from the WHO and work cooperatively to fight the coronavirus pandemic.

That will mean opting into Covax, a multilateral plan to distribute coronavirus vaccines that has drawn support from more than 170 nations but was spurned by President Donald Trump during his feud with the WHO.

Harris also spoke with the agency’s director general, Tedros Adhanom Ghebreyesus, according to the WHO. Tedros tweeted Thursday that he thanked Harris and Biden “for their commitment to @WHO and global health.”

The upbeat remarks, delivered on Biden’s first full day in office, signaled the new administration’s desire to restore the United States’ relationship with an organization it helped found and shape after months of WHO-bashing and threats — and the WHO’s apparent willingness to work with them.

“The United States stands ready to work in partnership and solidarity to support the international covid-19 response, mitigate its impact on the world, strengthen our institutions, advance epidemic preparedness for the future, and improve the health and well-being of all people throughout the world,” Fauci said.

Mending ties with the WHO is part of a broader push to restore U.S. leadership in global public health and reengage with traditional allies after four years of Trump’s “America First” foreign policy.

The Biden administration’s national covid-19 strategy, for instance, promises that the country will “rebuild health security alliances, elevate U.S. efforts to support the Global Health Security Agenda, and revitalize U.S. leadership.”

Fauci’s address represented a striking reversal of tone.

“I join my fellow representatives in thanking the World Health Organization for its role in leading the global response to this pandemic,” he said. “Under trying circumstances, this organization has rallied the scientific and research community to accelerate vaccines, therapies and diagnostics.”

Tedros thanked Fauci for his remarks and for recommitting to the covid-19 fight, calling it “a good day for the WHO and a good day for global health.”

“We have a lot of work to do, and lessons to learn, to end the pandemic and meet the long list of global health challenges we face — the world will be better able to meet them with you,” Tedros said.

The past year has been anything but easy for the WHO, which has been at the heart of a complex global health crisis as well as an acrimonious political conflict.

Trump was highly critical of the organization and its director general, accusing them of mishandling the initial outbreak and being too subservient to China.

In July, after months of threats, Trump issued a letter announcing the U.S. withdrawal from the WHO after a year. In September, the Trump administration announced it would not participate in Covax because of its link to the WHO.

Some elements of Trump’s critique have resonated beyond the White House. The WHO’s actions in the early days of the pandemic have also been criticized by an independent panel, for instance, and reform measures are under discussion.

But few supported the Trump administration’s undermining of the agency mid-pandemic, and Biden promised as a presidential candidate to reverse course. Hours after taking office, the new president signed directives to reengage with the WHO.

Questions about China are likely to remain front and center in the days ahead. Fauci on Thursday expressed support for WHO-led efforts to determine the origins of the pandemic with a mission sent to China, amid fears that Beijing will obstruct the agency’s efforts.

“The international investigation must be robust and clear,” he said. “And we look forward to evaluating it.”