Yahoo Inc says it's "going to take time" to thoroughly evaluate Microsoft Corp's unsolicited $45 billion offer keeping in mind its strategic options, including keeping the company independent.

It was undertaking a deliberate review of Microsoft's offer to pay Yahoo shareholders either $31 in cash, or 0.9509 of a share of Microsoft common stock, Yahoo said in a media release posted on the company Web site.

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."

"They're going to take time to thoroughly evaluate the proposal in the context of Yahoo!'s strategic plans including maintaining Yahoo! as an independent company.

"That process will take some time, but the board will ultimately pursue the option that it believes can best maximise value for our shareholders."

In response to a frequently asked question about whether Yahoo would seek proposals from other companies, the company said its board "is going to evaluate all of Yahoo!'s strategic alternatives and pursue the option that it believes can best maximise value for our shareholders".

In reply to another question about what would a deal like this mean for Yahoo's users, advertisers, publishers, partners and people, it said as the Yahoo's board is going to evaluate all aspects of this proposal it wouldn't be appropriate to speculate about the potential benefits or challenges of a deal.

By absorbing Yahoo, Microsoft hopes to gain the heft it has long sought with consumers, advertisers and other online publishers, providing access to roughly 500 million world-wide monthly users of Yahoo's Internet services. These range from email to online dating and help generate Yahoo's roughly 16 per cent share of total US online-ad revenue.

The bid is the biggest Internet-related deal since the 2001 merger between America Online Inc. and Time Warner Inc.