Mumbai: Media Mogul Rupert Murdoch has left the option for a joint bid with Microsoft Corporation to acquire Yahoo Inc open, days ahead of the 26 April deadline for Yahoo to respond to Microsoft's takeover offer..

Speaking to reporters after a speech at the Atlantic Council, an international affairs group based in Washington, Murdoch said he would not challenge a Microsoft bid for Yahoo!. "I certainly can't afford to bid against Microsoft," he said.

The News Corp chief, however, refused to rule out a possible deal with Microsoft over search engine provider Yahoo!. He merely said it all "depends on the deal."

Yahoo! has time until 26 April to respond to Microsoft's takeover offer.

Murdoch said Google is gaining influence in the advertising world. "Is Google really going to get control of the advertising world, and should Microsoft be supported in their attempt to try and stop that?" he asked.

Yahoo too is expected to report strong first quarter results, which could force Microsoft to raise its estimated $43 billion offer.

Yahoo, meanwhile, is pursuing a deal to merge with Time Warner Inc's AOL internet division. Yahoo is also planning tests with Google Inc on running a piece of Yahoo's web search ad sales.

Speculation has also been rife on a possible alliance between Murdoch and Microsoft over the Yahoo! takeover time.

Yahoo! is expected to release its first quarter results ahead of the deadline that Microsoft has set for its $42 billion bid for the company.

A better-than-expected results may help Yahoo! reassure its shareholders that the company has been undervalued by Microsoft, and pressure Microsoft to raise its offer.