Secretary of State John Kerry will join more than 100 countries in signing a climate change deal that the president agreed to last year in Paris, but it won't mean the landmark agreement is a done deal.

The State Department said on Wednesday that the Friday signing at United Nations headquarters, although a "big step," will not mean the agreement goes into effect.

A senior official described a provision in the deal that would allow for a country to withdraw, such as the next president of the United States.

The official described a distinction between "signing" the agreement, and actually "joining" the agreement. It takes 55 countries joining the agreement for it to go into effect, but the Earth Day signing will not cross that threshold even though 130 countries intend to sign. The actual joining will come later this year, the senior official told reporters on a call.

"We don't have, yet, a time" when the U.S. will join the agreement, the official said. The State Department must first complete work on finalizing an executive agreement to join the Paris agreement. That document will be finished this year.

Nevertheless, Friday is a "big deal" because it signals countries' intent to join the agreement, which means taking on all the obligations of reducing emissions under the Paris agreement.

The Paris agreement is a nonbinding accord among 196 countries to take steps to reduce greenhouse gas emissions to keep the average temperature of the Earth from rising 2 degrees Celsius over the next two decades.

Most scientists blame the burning of fossil fuels for increasing greenhouse gas emissions, resulting in more severe weather, glacier melting, ocean acidification, droughts and flooding.