Yahoo! has signed an exclusive three-year deal with Viacom to provide sponsored search and contextual ads to more than 170 websites including spin-offs from MTV, VH1 and Nickelodeon.

The online media company will provide the ads to around 33 key Viacom broadband websites initially and potentially a further 140 sites through its new Panama search marketing system, which launched earlier this year.

Viacom, which held a competitive pitch for the contract, said that the decision to choose Yahoo! over market leader Google was not influenced by the $1bn lawsuit the company is pursuing against the search engine's subsidiary YouTube.

The MTV owner previously used a mix of search marketing services from various online advertising providers, including Google.

This is the first time Viacom has signed an exclusive partnership deal across all of its web portfolio globally.

The deal is a big coup for Yahoo! in its bid to win media owners over to the merits of the new Panama system and increase its competitiveness in the online advertising space to close the gap on Google.

Yahoo! has lagged behind its rivals including Google, which scored a £900m deal to provide a similar service for social networking site MySpace last year.

The chief executive of Viacom, Philippe Dauman, said Yahoo! had made "impressive strides" with its new Panama system.

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