The UN chief told the world body's 193 member nations today that the ceremony will be a key step toward ratification of the agreement. Every UN treaty is first signed and then ratified.
The climate agreement needs to be ratified by 55 countries, representing at least 55 percent of greenhouse gas emissions, to enter into force.
Ban said he has issued invitations and the leaders of Peru, France and Morocco, who hosted the last three climate conferences, will attend.