BELLEVUE, Wash. — Microsoft Corp. chief executive officer Steve Ballmer said yesterday his company is no longer interested in buying all of Yahoo Inc., although he told shareholders that the company would still be “very open” to a collaboration on Internet search. His comments sent Yahoo shares diving by 19 percent.

“Let me be clear,” Ballmer said at Microsoft’s annual shareholder meeting. “We are done with all acquisition discussions with Yahoo.”

Yahoo spurned a $47.5-billion takeover offer from Microsoft in May, and later rejected Microsoft’s bid to buy only its search engine. Ballmer has said repeatedly of late that the buyout remains off the table, although a search-related deal is possible.

But yesterday marked the first time he had renewed that stance since the resignation announced this week by Yahoo CEO Jerry Yang, who had resisted Microsoft’s overtures. Yahoo shares rose when Yang said he would step aside, because investors hoped it meant a deal with Microsoft would now be more likely.

Ballmer said the companies are not currently talking about a search deal.

Yahoo shares plummeted $2.20 to $9.35 in afternoon trading, well below the $33 per share that Microsoft offered in May. Microsoft shares tumbled 57 cents, or 2.9 percent, to $19.02. The shares hit a 10-year low of $18.74 last week.

Michael McDonald, a shareholder who flew from Atlanta to attend the meeting, said he blames Microsoft’s run at Yahoo for depressing its share price and hopes the software maker doesn’t try again.

McDonald, a retired advertising executive, called the race to win in Web search and advertising “the dot-com bubble all over again. The economic period we’re in now is going to prove the questionable value of search.”

Instead, he said he’d rather see Microsoft cut employees and expenses, or spend cash to buy business software companies.

“We don’t need three Googles,” he said.

Some analysts have interpreted Ballmer’s public comments about a Yahoo buyout as negotiating posturing, and suspect Microsoft might still want to grab Yahoo at a low price, in hopes of improving their joint position in online search and advertising. However, analysts have also said Microsoft is likely to wait until next year before deciding, giving it time to watch Yahoo’s performance and study the antitrust regulatory climate in a new administration in Washington.

After rejecting Microsoft’s earlier offers, Yahoo entered an agreement with Google that would have put some of that company’s ads on Yahoo’s Web pages. Google backed away from the deal this month after the Justice Department threatened to block it. Yahoo expected the partnership to bring in as much as $450 million in operating cash flow in the first year.

Yahoo also has held talks with Time Warner Inc.’s AOL since April about a combination. An acquisition of AOL would bring more so-called display ads, such as banners, which are less lucrative than search ads.

Google and Procter & Gamble Co., the world’s largest consumer products company, have been working together to learn more about each other and about targeting customers.

P&G said yesterday it has done job swaps with Google and Google employees have been at P&G’s Cincinnati headquarters helping with training.

P&G spokeswoman Allison Yang said the company wants to reach more consumers who are increasingly online.

“This is all about learning,” she said. “It’s about putting consumers in connection with our products in the right spots.”

She said P&G has shared information with Google visitors about its consumer research, planning and operations. “The relationship will certainly continue, and we’ll continue looking at what the opportunities are,” Yang said.

Google officials said their employees learned a lot while “embedded” at P&G about the company’s culture, lingo and the history of its brands and strategies. They said they expect to keep up a dialogue with P&G about innovative ways they can work together.

Meanwhile, Ballmer attempted to reassure shareholders that Microsoft can thrive despite the economic downturn, citing the software maker’s long-term research-and-development spending and new products that mix desktop software and over-the-Internet computing.

When a shareholder, alluding to Microsoft’s languishing stock price, asked Ballmer when Microsoft’s best years would arrive, the CEO countered that every year is Microsoft’s best year. Then he jokingly added, “If we could get this economic thing headed in the right direction. ... I’m not going to pretend we have control over that. You’d better call D.C.”

With Bloomberg News reports