The Chinese Defense Ministry did not respond to e-mailed queries on the question.
The Pentagon said it was aware of reports predicting another test, but declined to comment on what it called “intelligence matters.”
“We monitor carefully China’s military developments and urge China to exhibit greater transparency regarding its capabilities and intentions,” Lieutenant Colonel Monica Matoush said.
Sources within the US government and outside experts said there was no immediate evidence pointing to the preparations for the type of satellite or rocket launches used by China for past anti-satellite tests at lower orbits.
However, they said that Beijing could test its anti-satellite weapons in other ways that would be harder to detect, such as by jamming a satellite’s signals from the ground or issuing a powerful electromagnetic pulse from one satellite to disable another.
China could also maneuver two satellites very close together at higher orbits, replicating actions it has already taken in lower orbits in August 2010 and November 2010. Such activities could be used to perform maintenance or test docking capabilities for human spaceflight, but could clearly be used for more destructive purposes as well, they said.
The US has continued to test its own anti-satellite capabilities. In February 2008, a missile fired from a US Navy cruiser in the north Pacific destroyed an ailing US satellite in orbit.
The US government said the satellite’s toxic fuel posed a risk upon re-entry of the Earth’s atmosphere. Skeptics said the test was a message to China.
Any further anti-satellite test by China would be troubling, especially if it occurred at higher altitudes, said Bruce MacDonald, a former White House official who is now a senior director at the US Institute of Peace.
The US operates its fleet of Global Positioning System (GPS) satellites in medium Earth orbit about 17,700km above the surface of the Earth, while US military communications and early missile warning satellites are in geostationary orbit 35,400km above the equator.
Brian Weeden, technical adviser for the nonprofit Secure World Foundation and a former US Air Force space and missile expert, said a Chinese anti-satellite test at those higher orbits would put US satellites at risk.
“Some critical US assets in that region have been assumed for the most part to be safe from those kind of attacks,” he said. “Such tests would signal that they’re not.”
Additional reporting by Mark Hosenball in Washington and Terril Yue Jones in Beijing