The World Health Organization chief on Monday urged countries to nail down a landmark global agreement on handling future pandemics after they missed a hard deadline.

Scarred by Covid-19 -- which killed millions, shredded economies, and crippled health systems -- nations have spent two years trying to forge binding commitments on pandemic prevention, preparedness, and response.

Negotiators failed to clinch a deal ahead of this week's World Health Assembly -- the annual gathering of WHO's 194 member states -- the deadline for concluding the talks.

WHO chief Tedros Adhanom Ghebreyesus opened the assembly Monday, saying he was confident that an agreement would be secured.

"Of course, we all wish that we had been able to reach a consensus on the agreement in time for this health assembly and crossed the finish line,” he said.

"But I remain confident that you still will because where there is a will, there is a way."

Tedros said the task before negotiators had been "immense, technically, legally, and politically", and that they had been "operating on a very ambitious timeline".

"You have demonstrated a clear commitment to reaching an agreement," he said, adding that negotiators had "worked long days and nights", closing meetings as late as 4:00 am.

He hailed their dedication to push forward despite "a torrent of misinformation that was undermining your negotiations".

While missing Friday's deadline, countries have voiced a commitment to keep pushing for an accord.

Negotiators are due on Tuesday to present the outcome of the talks to the assembly, which runs until June 1, and the assembly will take stock and decide what to do next.

"I know that there remains among you a common will to get this done, so, there must always be a way," Tedros said.

"Meaning the solution is in your hands," he stressed.

Parallel talks have also taken place on revising the International Health Regulations, which were first adopted in 1969 and constitute the existing international legally binding framework for responding to public health emergencies around the world.

The proposed amendments to the IHR, including adding more nuance to a system meant to alert countries to potential health emergencies of global concern, might have a better chance of being adopted during this week's assembly, observers said.