The FTC said the deal was "unlikely to substantially lessen competition" though it would be expected to create a formidable force in the rapidly growing online advertising field.
However, Google and DoubleClick, a New York-based firm that specializes in placing display ads on Web sites, still face substantial antitrust scrutiny in Europe, the Wall Street Journal said.
Google has said it will need European clearance before it will close the deal. The European Commission set an April 2, 2008, deadline for completing its review.
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