SAN FRANCISCO — Momentum seems to be shifting toward Microsoft Corp. in its high-stakes bid to buy Yahoo Inc., analysts said yesterday.

Although some Yahoo shareholders have called for Microsoft to raise its buyout offer, not all are yodeling for a much higher price. That's because nearly 90 percent of Yahoo's institutional shareholders, including most of the top 20, also hold Microsoft stakes, according to report released by RiskMetrics Group, a financial risk-management company.

Microsoft shareholders have good reason to urge the software giant not to overpay by dramatically sweetening its bid.

Consider Yahoo's largest investor, Capital Group's Capital Research Global Investors and Capital World Investors. The Los Angeles-based investment company owned 523.6 million Microsoft shares as of Dec. 31, compared with 154.8 million Yahoo shares.

That kind of dual ownership has short-circuited Yahoo's efforts to squeeze a higher bid from Microsoft, which made its unsolicited $31-a-share takeover offer two weeks ago.

What's more, after watching Microsoft's stock sink 13 percent since then on concern about potential trouble integrating the two companies, some of its shareholders would be happy if Microsoft walked away.

Meanwhile, Yahoo seems to be running out of alternatives. No competing bids have emerged. News Corp. appears to be the last option on a shrinking list being considered by Yahoo as a means of evading Microsoft's clutches.

Bear Stearns analyst Robert Peck said none of the other options — a tie-up with Time Warner's AOL or farming out its search business to Google Inc. — was viable. He and other analysts said a combination with Microsoft was the most likely outcome.

"Microsoft needs Yahoo but not as much as Yahoo needs Microsoft," investment banker Ken Marlin said.

That said, he added, "no one believes that the current offer on the table is the best and final Microsoft offer."

Yahoo's board Monday rejected Microsoft's offer, then worth $44.6 billion, saying it undervalued the company. Microsoft countered that its offer was "full and fair." Analysts expect Microsoft ultimately to offer $35 or $36 a share to clinch the deal.

Shareholders such as Yahoo's second largest, Legg Mason, have urged Microsoft to raise its offer. But the stock market response to the deal indicates that Microsoft investors worry about paying too much for Yahoo, RiskMetrics Group said. Most institutional investors will pressure Yahoo to hold out for a little more to save face but get far less than the $40 a share that Yahoo and its bankers reportedly are seeking.

While some analysts expect more brinkmanship, Jackson Securities analyst Brian Bolan expects Microsoft to make its move sooner rather than later — if only to prevent more Yahoo employees from defecting.

Recruiters are circling Yahoo. San Francisco start-up Xobni Corp. yesterday announced it had hired Jeff Bonforte, Yahoo's vice president of social search, as its CEO. Earlier in the week, Google lured away Bradley Horowitz, who had led a Yahoo division in charge of creating innovative products.