BEIJING, Oct. 16 (Xinhuanet) -- U.S. space agency NASA has added its voice to congratulations being sent to Chinese mission controllers following the launch Wednesday of China's first astronaut.

Applauding the successful launch, NASA Administrator Sean O'Keefe said in a statement that 38-year-old Yang Liwei's flight into space was "an important achievement in the history of human exploration."

"The Chinese people have a long and distinguished history of exploration," O'Keefe said.

"NASA wishes China a continued safe human space flight program," he added.

Although Wednesday's launch makes China only the third nation after Russia and the United States to have put a man into space, the Chinese achievement comes at a difficult time for NASA.

Following the loss of the shuttle Columbia in February, the U.S. manned space program is grounded with no clear indication yet as to when it will resume.

Officials have said they expect to resume flights next year, but the earliest date thought likely for a return to flight is not until September 2004.

Without its remaining three shuttles in operation ,NASA is having to rely on Russian space launches to ferry crew replacements and supplies to the orbiting International Space Station.

It has no other operational vehicle capable of carrying humans into orbit and the success of the Chinese launch is likely to spur efforts to develop a shuttle successor. (CNN)