Although earlier reports have indicated Microsoft was close to a deal with online advertising firm DoubleClick, sources now say Google is emerging as a top contender as the price of the company continues to grow.

The Wall Street Journal said Monday that as the likely acquisition price surpassed the $2 billion mark, Microsoft has been slow in responding with a counter offer. Negotiations were described as "fluid," although a deal could be announced in days.

Google and Microsoft are locked in an increasingly bitter battle for Internet advertising dollars. While Google is no doubt the behemoth in Web ads, Microsoft has made motions to make up lost ground, such as its adCenter offerings.

Much of the interest around DoubleClick likely has to do with concerns over Google's dominance in the industry. DoubleClick has large customers, including the AOL network and MySpace, and a Google buy would strengthen the company's hold on Web advertising.

Neither Google, Microsoft, nor DoubleClick were returning requests for comment on Monday.