A Japanese entertainment group has asked the popular video-sharing site YouTube Inc. to come up with a system that will prevent users from uploading videos that would infringe on copyrights, a group spokesman said Tuesday.

The Japan Society for Rights of Authors, Composers and Publishers sent a letter making the request to YouTube cofounders Chad Hurley and Steve Chen by express mail and e-mail on behalf of 23 Japanese TV stations and entertainment companies, according to Takashi Fujii, a spokesman for the group.

Most of the videos posted on YouTube are homemade, but the site also features copyrighted material posted by individual users.