Microsoft CEO Steve Ballmer is taking his company's $45 billion bid to acquire Internet portal Yahoo public after being rejected last year, saying it is in the best interest of both firms to better compete in the online market.

He made the assertion this morning during a conference call with analysts after the Redmond, Washington software giant announced an unsolicited proposal to acquire Yahoo, Inc. in a stock and cash deal worth $44.6 billion.

Last night I called Jerry Yang to discuss our proposal, Ballmer said, referring to Yahoo's CEO. This is a proposal we believe to be a very good deal for Yahoo! shareholders and an offer we want them to think about seriously, to be excited about, and particularly to have the Yahoo! employees be very, very excited about.

Yahoo issued a statement today saying it will evaluate the proposal carefully and promptly.

Ballmer said in a letter to Yahoo's Board on Thursday that then Yahoo Chairman and CEO Terry Semel rejected a proposed buyout offer in February of 2007 after the companies had discussed various commercial partnerships starting at the end of 2006.

A year ago the Yahoo! management team told us it wasn't really the right time to discuss an acquisition, Ballmer said. That is why we are making it public today so both sets of shareholders, employees and customers can understand the incredible opportunity in a combination of Microsoft and Yahoo.

The bid for Yahoo comes as Internet search leader Google has taken a commanding lead in the online search market. According to Internet researcher comScore, Google sites currently have 58 percent of all core searches, followed by Yahoo! sites at 22.4 percent and Microsoft sites at 9.8 percent.

Today this market is increasingly dominated by one player, Microsoft said in statement. Together, Microsoft and Yahoo! can offer a competitive choice while better fulfilling the needs of customers and partners.