News Corp. and NBC Universal will launch a free online video site this summer, featuring full-length movies and television shows in a challenge to YouTube.

The move underscores how serious a threat YouTube has become to media companies, which fear losing a new generation of viewers who are as likely to be found in front of computers as television screens. Another media company, Viacom Inc., has sued Google for $1 billion over unauthorized use of its videos on YouTube.

The first partners that will distribute the platform will be Yahoo Inc., Microsoft Corp., AOL and MySpace. The advertisers in this new web site will be companies like Cadbury Schweppes Plc, Cisco Systems Inc. and General Motors.

While NBC Universal and News Corp. compete fiercely for TV and movie audiences globally, their partnership shows the risks executives will take to regain control over content as more consumers turn to YouTube or Apple Inc.'s iTunes.