GENEVA (Reuters) -The head of the World Health Organization on Monday voiced confidence that countries would one day reach a deal on a pandemic accord after failing to produce an agreement last week.

Health officials from the WHO's 194 member states are seeking to wrap up more than two years of negotiations on new rules for responding to pandemics during the May 27-June 1 World Health Assembly in Geneva.

However, the top prize, a legally-binding pandemic treaty to shore up the world's defences against future pathogens after COVID-19 killed millions, has proved elusive and negotiators failed to produce a draft deal on Friday for formal approval by the assembly this week.

"Of course, we all wish that we had been able to reach a consensus on the agreement in time for this health assembly, and cross the finish line," Director-General Tedros Adhanom Ghebreyesus said in his opening address.

"I remain confident that you still will, because where there is a will, there is a way. I know that there remains among you a common will to get this done."

Negotiations are still ongoing for an update to existing health rules on outbreaks and negotiators say that a deal is close.

(Reporting by Gabrielle Tetrault-Farber and Emma Farge; Editing by Sriraj Kalluvila)