Microsoft Corp and Yahoo Inc have agreed to an online search and advertising partnership, in an attempt to rival Google Inc, that will be announced within 24 hours, a source familiar with the situation said on Thursday.

Microsoft will not pay an upfront fee to Yahoo, and the focus of the deal is on sharing revenue between the two companies, said the source, who did not want to be identified because a formal announcement has not been made.

Microsoft tried to buy Yahoo last year but its $47.5 billion bid was rebuffed and Yahoo's attempt to seal a search advertising deal with Google Inc fell apart under regulatory scrutiny. Microsoft's new Bing search engine will power Yahoo's searches, according to Advertising Age, while Yahoo will handle the advertising sales, using Microsoft technology.

The deal should give Bing a giant boost in competing with Google's search engine. Google's search engine dominates the marketplace with 65 percent of U.S. Internet searches, according to figures provided by research firm ComScore. Last month, Microsoft had only 8.4 percent of the market and Yahoo 19.6 percent.

There is a chance a deal combining the powers of the second and third-ranked search engine companies would be blocked by antitrust regulators. Google and Yahoo dropped plans for an advertising partnership last year under opposition from the U.S. Department of Justice.

Shareholders of both Microsoft and Yahoo have been urging the two to strike a deal for some time. Earlier this month, activist investor Carl Icahn, who owns about 5 percent of Yahoo and is a director on its board, spoke out in favor of a search deal, as talks between the two companies appeared to regain momentum.

Shares of Yahoo traded at $17.39 in after-hours trading after closing at $17.22, while shares of Microsoft rose to $23.51 in after-hours trading from their close of $23.47.