SHANGHAI (Reuters) -- U.S. President Barack Obama has said that both Washington and Beijing must take "critical steps" to tackle global climate change.
Other countries are waiting to see what the United States and China will do ahead of a UN meeting in Copenhagen, Obama said.
China is considered the world's biggest annual emitter of carbon dioxide, the main greenhouse gas from human activity.
But Beijing has said developing countries should not accept internationally binding ceilings on emissions while they focus on economic growth and escaping poverty.
China has said rich economies, with their far higher average emissions per person, must lead the way in cutting emissions and giving more economic and technological help to developing countries threatened by global warming.