SEATTLE, USA: Yahoo Inc said it may take "quite a bit of time" to weigh its strategic options, including keeping the company independent, following Microsoft Corp's $45 billion offer to buy the company.

In a weekend posting on the company's Web site, Yahoo said it was undertaking a deliberate review of Microsoft's unsolicited offer to pay Yahoo shareholders either $31 in cash, or 0.9509 of a share of Microsoft common stock.

The review "will include evaluating all of the Company's strategic alternatives including maintaining Yahoo! as an independent company," the posting said. "A review process like this is fluid, and it can take quite a bit of time."

In response to a frequently asked question about whether Yahoo would seek proposals from other companies, also posted on its Web site, the company said it was going to evaluate all options.

Analysts cited Comcast Corp, Viacom Inc and General Electric Co among possible bidders, although they also said few companies had the balance sheet to compete with Microsoft or were as natural a fit for Yahoo.

Microsoft's bold move to buy the Silicon Valley company would create a combined entity better able to respond to the growing dominance of Google Inc in Web search and digital advertising.

Microsoft said it has courted Yahoo for the last 18 months, but its earlier approaches were rebuffed and it decided to make its offer public to Yahoo shareholders.

Yahoo shares shot up about 48 percent to $28.33 on the news of Microsoft's offer.