UNITED NATIONS — The official in charge of global climate negotiations says between 80 and 100 countries are expected to sign the landmark agreement to tackle climate change reached in Paris in December at a ceremony at U.N. headquarters on April 22.

Segolene Royal, French environment minister and newly-appointed president of U.N.-led climate negotiations, said Friday that more than 30 heads of state and government have already said they will attend signing event. She said invitations signed by U.N. Secretary-General Ban Ki-moon, French President Francois Hollande, and herself are also being sent again to all world leaders.

“I will, of course, work very hard so that we get these 80 to 100,” Royal told reporters after meeting Ban. “We might have more which would be fantastic.”