MOUNTAIN VIEW, Calif. - Google Inc. (Nasdaq:GOOG) says it will help European regulators prove Microsoft Corp. (Nasdaq:MSFT) has stifled competition and innovation by bundling its popular Web browser with the Windows operating system.

The decision to back the European Commission, announced Tuesday by the search-engine company, isn't a surprise because Google wants to lessen the dominance of Microsoft's Internet Explorer with a competing Web browser called Chrome.

However, Google's involvement in the European Commission proceedings figures to inject more bad blood between the two rivals.

Microsoft intensified the rancour last year by spearheading a successful campaign to scuttle a proposed online advertising partnership between Google and Yahoo Inc. (Nasdaq:YHOO).