Microsoft offered to buy search engine operator Yahoo for $44.6 billion in cash and stock in a move to boost its competitive edge in the online services market.

Microsoft bid $31 per share for Yahoo, representing a 62 percent premium to Yahoo's closing stock price Thursday. The company expects the proposed transaction to be completed in the second half of calendar year 2008.

Microsoft said that its proposal would allow the Yahoo! shareholders to elect to receive cash or a fixed number of shares of Microsoft common stock, with the total consideration payable to Yahoo! shareholders consisting of one-half cash and one-half Microsoft common stock.

Yahoo! described Microsoft's proposal as "unsolicited" and said that its Board of Directors will evaluate this proposal carefully and promptly in the context of Yahoo!'s strategic plans.

"We have great respect for Yahoo!, and together we can offer an increasingly exciting set of solutions for consumers, publishers and advertisers while becoming better positioned to compete in the online services market," said Steve Ballmer, chief executive officer of Microsoft. "We believe our combination will deliver superior value to our respective shareholders and better choice and innovation to our customers and industry partners."

Microsoft is feeling increasing pressure to compete with Google, which plans to beef up its portfolio with a $3.1 billion purchase of online advertising company DoubleClick.

Microsoft currently trails both Yahoo and Google in the lucrative and growing business of Web search.

"The combination will create a more efficient company with synergies in four areas: scale economics driven by audience critical mass and increased value for advertisers; combined engineering; operational efficiencies through elimination of redundant cost; and the ability to innovate in emerging user experiences such as video and mobile," microsoft said. Te company believes these four areas will generate at least $1 billion in annual synergy for the combined entity

Microsoft has developed a plan and process that will include the employees of both companies to focus on the integration of the combined business.

Microsoft believes this proposed combination would receive all necessary regulatory approvals and expects that the proposed transaction would be completed in the second half of calendar year 2008.