An imprisoned 72-year-old Chinese dissident is to be released this week after more than six years behind bars for helping to organize a would-be opposition party, a U.S. activist group said Wednesday.

The release comes in advance of a trip to the United States by Chinese President Hu Jintao next month, but there was no indication it was meant as a gesture to Washington.

Tong Shidong, a physics professor, was due to be freed Thursday, according to the Dui Hua Foundation in San Francisco, which researches Chinese prisons and has helped to arrange other prisoner releases. It cited information from the Chinese Justice Ministry.

Tong was detained on June 10, 1999, and later convicted of subversion for organizing a branch of the opposition China Democracy Party at Hunan University in southern China, the group said. He also edited a political journal called "Opposition Party."

He was sentenced to 10 years, but the announcement Wednesday said that was reduced by 39 months due to good behavior and his age.

Detained with Tong was Liao Shihua, a Hunan labor organizer who also helped to produce the political magazine, according to human rights groups. Liao served his full six-year sentence and was released in June, the Dui Hua Foundation said.