The US and Russia have been cooperating in space for a long time, going back to the Apollo-Soyuz Test Project. For several years American astronauts took tours of duty on the Russian Mir space station and it and the Shuttle were outfitted with compatible docking equipment. Cooperation continues, with ups and downs, on ISS.

I think the Russians are willing to work with almost anybody who has the cash. Space privatization's become a necessity for the Russians. It's my understanding that the Chinese manned program is based on a technology transfer from Russia--the Chinese are basically flying Soyuz spacecraft they built themselves from Russian blueprints. The Chinese program thus starts out highly compatible with Russian hardware, so it seems to me like a collaboration between the two is more natural than a collaboration between us and Russia.