WASHINGTON — China and India formally agreed Tuesday to join the international climate change agreement reached in December in Copenhagen, the last two major economies to sign up.

The two countries, among the largest and fastest-growing sources of greenhouse gas emissions in the world, submitted letters to the United Nations agreeing to be included on a list of countries covered by the Copenhagen Accord, a three-page nonbinding statement reached at the end of the contentious and chaotic 10-day conference.

China and India join 107 countries that have signed up under the accord, which calls for limiting the rise in global temperatures to no more than 2 degrees Celsius, or 3.6 degrees Fahrenheit, beyond pre-industrial levels.

The agreement also calls for spending as much as $100 billion a year to help emerging countries adapt to climate change and develop low-carbon energy systems, to bring energy technology more quickly to the developing world and to take steps to protect tropical forests from destruction.