US, China formally join global climate pact

The United States and China have formally joined the sweeping global climate change agreement reached in Paris last year.

President Barack Obama and Chinese President Xi Jinping delivered documents to U.N. Secretary-General Ban Ki-moon entering their countries into the pact during a ceremony Saturday on the sidelines of the Group of 20 major economies summit in Hangzhou, China. The document certifies that the countries have taken all necessary domestic steps needed to join the agreement.

Obama says the United States is committed to being a global leader in the fight against climate change. He says the Paris Agreement may be remember as "the moment we finally decided to save our planet."

Xi called the agreement a milestone that marks the "emergence of a global government system" for climate change.

The agreement will come into force after a critical mass of polluting countries has joined. The U.S. says it's hopeful that will happen this year.