President Barack Obama says a decision by the U.S. and China to formally join a landmark climate agreement may be seen as ``the moment that we finally decided to save our planet.''

Obama says there was ``no shortage'' of cynics who doubted an agreement would ever be reached.

But he says leadership by the U.S. and China has been one of the biggest drivers of action on the issue, which Obama has highlighted during his presidency. Obama said cooperation is ``the single best chance that we have'' to save the planet because no one country can go it alone

Many more countries must formally join the agreement for it to take effect.

Obama spoke Saturday after meeting with Chinese President Xi Jinping (shee jihn-peeng) in the Chinese coastal city of Hangzhou. He called for full implementation of the agreement to prevent or delay the worst effects of climate change.  (Associated Press)