system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is China building a space station of their own instead of collaborating with other countries?
gpt
China had expressed interest in joining the International Space Station project in the past, but the United States had blocked them on fears that they would take the technologies they would gain from the experience for military purposes.

Please note that Russia is allowed to participate in the ISS despite similar concerns previously.