May 18 (Bloomberg) -- Microsoft Corp.'s plan to buy AQuantive Inc. for $6 billion increases the likelihood that the software maker will also buy Yahoo! Inc., Goldman Sachs Group Inc. analyst Anthony Noto said today.

Yahoo would plug a ``strategic hole'' at Microsoft that isn't filled by the purchase of AQuantive, announced today, Noto said in a note to clients. AQuantive, which creates Web ads and measures whether they reach the target audience, doesn't give Microsoft the roughly half a million advertisers required to compete against Google Inc., Noto said.

``We believe the odds of a deal happening over time actually increases,'' New York-based Noto wrote. ``Microsoft is willing to do deals that are a strategic necessity.''

Shares of Sunnyvale, California-based Yahoo rose $1.18, or 4.1 percent, to $29.75 at 4 p.m. in Nasdaq Stock Market trading. They have risen 16 percent this year.

Yahoo, owner of the most-visited U.S. Internet site, and Microsoft, the world's biggest software maker, have held talks about a partnership for Web search and ad programs, people briefed on the discussions said this month. Yahoo shares jumped as much as 19 percent on May 4 on reports that Microsoft wanted to buy the company.

Is Yahoo Willing?

Whether Redmond, Washington-based Microsoft buys Yahoo depends on whether Yahoo is willing to sell, Noto wrote. Yahoo spokeswoman Joanna Stevens and Microsoft spokesman Adam Sohn declined to comment.

Microsoft shares, up 3.3 percent this year, dropped 15 cents to $30.83. AQuantive surged 78 percent to $63.79 after the announcement that Microsoft plans to pay $66.50 a share in cash for the company.

For some other analysts, Microsoft's plans make a purchase of Yahoo less likely. While the deal shows Microsoft's commitment to online advertising, it may take months to incorporate AQuantive's operations, Merrill Lynch & Co. analyst Justin Post wrote today in a note.

That would make a purchase of Yahoo less likely within the next three months, he said.

``We have yet to identify a number two buyer that could get the same synergies or strategic value with Yahoo that we can envision with Microsoft,'' San Francisco-based Post wrote.

ValueClick

Shares of ValueClick Inc., the Internet's second-biggest advertising broker, rose $2.12, or 7.6 percent, to $30 in Nasdaq trading. The shares touched their highest ever value in intraday trading since the company's initial public offering in 2000.

Consolidation in the online ad industry and products from Google and Yahoo for selling ads in online auctions may pressure Westlake Village, California-based ValueClick to sell itself, Richard Fetyko, an analyst Merriman Curhan Ford & Co., wrote today in a note to clients.

Potential suitors for ValueClick may include IAC/Interactive Corp., New York-based Fetyko said. IAC, the Internet and media company assembled by billionaire Barry Diller, owns sites including Ask.com and LendingTree.com.

ValueClick spokesman Gary Fuges didn't immediately return a call seeking comment.

To contact the reporter on this story: Jonathan Thaw in San Francisco at jthaw@bloomberg.net

Last Updated: May 18, 2007 18:20 EDT