MTV parent Viacom Inc. said on Tuesday that it was suing Google Inc. and its Internet video-sharing site YouTube for more than $1 billion over unauthorized use of its programming online.

The lawsuit, the biggest challenge to date to Google's ambitions to make YouTube into a major vehicle for advertising and entertainment, accuses the Web search leader and its unit of "massive intentional copyright infringement."

Viacom filed the suit with the U.S. District Court for the Southern District of New York, seeking more than $1 billion in damages and an injunction against further violations.

Viacom contends that almost 160,000 unauthorized clips of its programming have been uploaded onto YouTube's site and viewed more than 1.5 billion times.

"YouTube's strategy has been to avoid taking proactive steps to curtail the infringement on its site," Viacom said in a statement. "Their business model, which is based on building traffic and selling advertising off of unlicensed content, is clearly illegal and is in obvious conflict with copyright laws."

Viacom said its decision to sue Google followed "a great deal of unproductive negotiation" with the company.

Representatives for Google and YouTube were not immediately available.

Google shares fell 0.8 percent to $451.12 in early Nasdaq trade. Viacom Class B shares were down 1 percent at $39.15 on the New York Stock Exchange.