Microsoft wants to boost its internet presence
Microsoft saw its shares fall 6% after it posted a fall in quarterly profits and earnings forecasts at the lower end of market expectations.
A day earlier the firm said profits fell 11% to $4.39bn (£2.22bn) in the first three months of the year.
Uncertainty about what will happen to the firm's $44.6bn-bid for Yahoo has added to market concerns.
Microsoft had given Yahoo until 26 April to respond but later implied it would wait a few days.
The deadline was due to expire on Saturday but by close of trade on Friday there had been no further statement from Microsoft.
Analysts now predict that the firm will either improve its offer, or try to replace Yahoo's board.
This second option would entail what is called a proxy battle - effectively embarking on a hostile bid.
Yahoo's board of directors has said that Microsoft's offer undervalues the firm, and that it would not accept anything less than $45bn.
While some analysts argue that Microsoft will now abandon the deal, others say it is unlikely to favour that option.
"We still believe Microsoft is committed to completing the transaction and is unlikely to walk away," said Citigoup analyst Brent Thill.
A day earlier Chris Liddell, Microsoft's chief financial officer, said: "With or without a Yahoo combination, Microsoft is focused on the online advertising market."
While Yahoo has opposed the Microsoft bid, it has looked into other options to improve its fortunes, including a possible tie-up with Time Warner's AOL.
But analysts say such an association would be a less strong partnership than one with Microsoft.
Shares in Microsoft ended at $29.9, after closing 6.1% lower, while Yahoo shed 1.8% to end at $27.