The U.S. wants to smash the satellite before it enters Earth's atmosphere with a single missile fired from the northern Pacific Ocean.
But the official Xinhua (shin-wah) News Agency reports that China's foreign ministry has warned the U.S. to avoid damaging security in space and in other countries.
China says it's keeping an eye on the situation and "working out preventative measures."
Russia has also voiced worries, saying it may really be a test of America's missile defense system. The U.S. says that's not the case.
U.S. diplomats have been instructed to tell governments that the operation is meant to protect people from the satellite's blazing descent and its toxic fuel.