Google's $1 billion acquisition of the mobile mapping app Waze is officially under review by the Federal Trade Commission (FTC), the Wall Street Journal reported.

The deal was completed in mid-June, but the FTC can review such deals even after they close. The initial agreement was not large enough to trigger an automatic review, but if Google gains an unfair advantage with the acquisition, the deal will be reversed.

In order for the FTC to block the deal, it would have to find evidence that Google's competitors would be significantly hampered. Sources told the Journal it is unlikely that the FTC will reverse the deal.

The antitrust review would also have to determine if Waze could become a legitimate competitor to Google maps.

Both Google and the FTC declined to comment on the current review.

Immediately after news of the acquisition broke, Consumer Watchdog, a nonprofit consumer and taxpayer advocate, urged the FTC to block the deal. In letters sent to both the FTC and to the U.S. Department of Justice, the consumer company vehemently contended the acquisition.

"Google already dominates the online mapping business with Google Maps," wrote John Simpson, Consumer Watchdog's Privacy Project director. "The Internet giant was able to muscle its way to dominance by unfairly favoring its own service ahead of such competitors as MapQuest in its online search results."

The Clayton Act is an antitrust law prohibiting acquisitions of companies by another that "might substantially lessen competition or tend to create a monopoly in any line of commerce."

Simpson also said in the letter that the acquisition would "allow Google access to even more data about online activity in a way that will increase its dominant position on the Internet."

In May's All Things Digital Conference, Waze CEO Noam Bardin said Google was its biggest competitor in the mobile maps market.

"What search is for the Web, maps are for mobile," he said. "We feel that we're the only reasonable competition to [Google] in this market of creating maps that are really geared for mobile, for real-time, for consumers-for the new world that we're moving into."

Waze generated enormous popularity - 45 million users in 190 countries - for its unique crowdsourcing feature that updates drivers on traffic congestion, roadblocks and accidents in real time.

Facebook and Apple were also reported suitors but dropped out for different reasons, leaving Google to make the purchase.