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 by April 22.

Segolene Royal, French environment minister and newly-appointed president of UN-led climate negotiations, said that more than 30 heads of state and government have already said they will attend signing event.

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She said invitations signed by UN 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.”

Royal said every country has developed a plan to fight climate change and on April 22 they will be explaining what they have done so far.

The Paris Agreement must be ratified by at least 55 countries representing at least 55 per cent of global greenhouse gas emissions to enter into force.

It sets a collective goal of keeping global warming below two degrees Celsius to pre-industrial times, and to pursue efforts to limit the temperature rise to 1.5 degrees Celsius.

The pact requires all countries to submit plans for climate action and to update them every five years, though such plans are not legally binding.

Royal said the signing ceremony is one of a series of events designed to keep up the momentum created in Paris when the agreement was reached.

US President Barack Obama was a key figure, along with China’s president, in spurring support for the climate deal.

Royal sidestepped a question asking whether she was concerned that the United States might pull out of the agreement if one of the Republicans who oppose the accord makes it to the White House.

She said support from the Obama administration and US involvement has been very important.