Thirty-one countries formally joined the Paris climate change pact Wednesday, bringing the total number of countries ratifying the treaty to 60 and raising hopes that it will enter into effect by the end of the year.

The number is higher than the 55-country threshold needed for the treaty to enter into force. But because together those countries account for just under 48 percent of total global emissions — short of the 55 percent threshold — the agreement isn't expected to take effect until later this year.

"I am convinced that the Paris Agreement will enter into force before the end of 2016," Secretary-General Ban Ki-moon said at an event on the sidelines of the high-level U.N. General Assembly gathering.

U.S. Secretary of State John Kerry said he is confident of reaching the magic number before the next U.N. climate conference, which starts Nov. 7 in Marrakech, Morocco. He urged people everywhere "to become warriors for the planet."

The world's two biggest emitters, the United States and China, have already ratified the deal. Brazil, Mexico and Argentina were the largest emitters to join the treaty Wednesday.

Many of the countries that joined were small island nations, whose very existence is threatened by rising sea levels provoked by global warming, but whose individual emissions account for a mere fraction of a percent of total global emissions.

The treaty's ratification has taken place at what is considered a blistering pace for international diplomacy, reflecting a sense of urgency in the fight against global warming and a desire to seal the deal before Ban and U.S. President Barack Obama leave office.

After years of negotiations, governments agreed in Paris last December to curb the emissions of carbon dioxide and other greenhouse gases that scientists say are warming the planet.

More than 170 world leaders have signed the deal.