Geneva, Switzerland - The head of the World Health Organization insisted on Monday it was "now or never" to strike a landmark global accord on tackling future pandemics, despite the US withdrawing from negotiations.

WHO director-general Tedros Adhanom Ghebreyesus said no country could protect itself from the next pandemic on its own – three days after US President Donald Trump's administration formally told the United Nations health agency it would play no further part in the pandemic agreement talks.

"We are at a crucial point as you move to finalize the pandemic agreement in time for the World Health Assembly" in May, Tedros told WHO member states at the opening of the week-long 13th round of negotiations at the organization's Geneva headquarters.

"It really is a case of now or never. But I am confident that you will choose 'now' because you know what is at stake."

Tattoos Tattoo addict "Black Alien" gets bloody tears inked under his eyes

A further one-week session is planned to finalize the agreement before the WHO's annual decision-making assembly.

In December 2021, fearing a repeat of the devastation wrought by Covid-19 – which killed millions of people, crippled health systems, and crashed economies countries decided to draft a new accord on pandemic prevention, preparedness, and response.

While much of the draft text has been agreed upon, disputes remain over some key provisions, notably over sharing access to pathogens with pandemic potential and then equitably sharing the benefits derived from them, such as vaccines, tests, and treatments.

"You remember the hard-won lessons of COVID-19, which left an estimated 20 million of our brothers and sisters dead, and which continues to kill," Tedros said.

"They are why we are here – to protect future generations from the impact of future pandemics," he continued.

"The next pandemic is a matter of when, not if. There are reminders all around us – Ebola, Marburg, measles, mpox, influenza, and the threat of the next disease X."

Food National Drink Wine Day: How to make homemade wine... the easy way!

Hours after returning to office on January 20, Trump signed an executive order to start the one-year process of withdrawing from the WHO, an organization he has repeatedly criticized over its handling of COVID-19.

The order also said that during the withdrawal process, Washington would "cease negotiations" on the pandemic agreement.

Tedros said Washington had formally notified the WHO on Friday of its withdrawal from the agreement talks.

"No country can protect itself by itself. Bilateral agreements will only get you so far," Tedros said, adding that prevention, preparedness, and response were the responsibility of all countries.

"Like the decision to withdraw from WHO, we regret this decision and we hope the US will reconsider," he said.

While much of the draft text has been agreed upon, disputes remain over sharing access to pathogens with pandemic potential and the sharing of benefits derived from them – vaccines, tests, and treatments.

Talks co-chair Precious Matsoso expressed hope that the proposed new wording would ensure a breakthrough.

"Let's make sure that the three years that we've spent does not end up being regretted – that we wasted three years of our time," she said.