The BBC has reported on a Chinese aircraft carrier that is currently under construction. The carrier is an old Admiral Kuznetsov class that was never fully constructed due to the collapse of the Soviet Union.
Is it a threat? Unlikely for for now, as the U.S have far more military might, although times are changing. China is set to become the Worlds largest economy in the next 10-20 years, overtaking the U.S.
Here's a comparison of various worldwide aircraft carriers:(Click to enlarge to non-blurry version)