SAN FRANCISCO — Yahoo Inc.'s board plans to reject Microsoft Corp.'s $44.6 billion bid to buy the Internet pioneer, The Wall Street Journal reported on its website Saturday.

Board members concluded the unsolicited offer massively undervalues the company, a person familiar with the situation told the newspaper.

The $31 per share bid was made public on Feb. 1. Board members so far would only say they were studying the offer.

Yahoo's board intends to send a letter to Microsoft on Monday explaining its decision, persons close to the company said.

Microsoft and Yahoo representatives did not immediately return calls for comment.

The slumping Internet company's rejection of the offer might mean Yahoo is getting ready for a long battle, analysts said.

Board members believe Microsoft is attempting to take advantage of a recent slump in share price to take over. But they're not ready to consider any offer below $40 per share, according to a person knowledgeable about the discussions.

Yahoo appears to be counting on Microsoft's reluctance to engage in a hostile takeover.

Ignoring the wishes of management and the board and creating resentment among the web giant's engineers could also make it harder to push the deal past authorities, as Yahoo officials could try to convince regulators that the deal is anticompetitive.

But analysts are uncertain whether Microsoft would be up to paying the higher price per share, which would raise its bid by about $12 billion.