GENEVA, Switzerland (AFP) —An extra week of negotiations to complete the crucial missing piece of an international agreement on handling future pandemics kicks off Monday at the World Health Organization (WHO), with sharp divisions holding up an accord.

Wealthy countries and developing nations are at loggerheads in the WHO talks over how the pandemic treaty, adopted last year, will work in practice.

The agreement’s Pathogen Access and Benefit-Sharing system deals with sharing access to pathogens with pandemic potential, then sharing the benefits derived from them: vaccines, tests and treatments.

“Developing countries are voicing their mistrust, fearing they will share their viruses without any guarantees of equitable access to vaccines in the event of a crisis,” WHO chief scientist Sylvie Briand told Agence France-Presse.

Meanwhile, other countries are asking whether the pharmaceutical industry would have the capacity and motivation to contribute to a global pandemic agreement “without a guarantee of return on investment,” she said.

Another challenge, she said, was “to integrate the sharing of genetic data, now as crucial as that of physical viruses for developing vaccines, treatments and diagnostics.”