Europe's competition regulator is moving ahead with formal antitrust charges against Google, according to The Wall Street Journal.
The charges relate to a five-year investigation in which the European Commission has probed into Google's business practices. The case hinges on whether Google uses its dominance as a search engine to promote its own services -- like YouTube or the Google+ social network -- unfairly over the services of competitors.
The charges set off the EU's most high-profile antitrust case since the commission went after Microsoft in 2004.
The investigation underscores Google's wide-ranging influence and the worries among regulators about how the search giant exerts its power. Google holds 90 percent of the Internet search market in Europe.
The commission is also expected to open a separate investigation examining Google's Android software, the most popular mobile operating system in the world. The commission will look into whether the company imposes unfair terms on handset makers that favor its own apps, like YouTube, over others, according to the Financial Times.
"This is obviously very disappointing news, especially for the search team that has worked so hard to create a great experience for our users over the last 16 years," Google said in a memo to employees, according to Recode.
The memo said Google has a "very strong case" for both investigations. The company did not respond to CNET's request for comment.
The EU's competition chief, Margrethe Vestager, made the decision Tuesday after consulting with European Commission President Jean-Claude Juncker, the Journal said.
For Google, the charges could mean paying up to 10 percent of the company's global sales, or more than $6 billion.
The EU's probe of Google began in 2010 but has repeatedly stalled because the company and the commission could not agree on settlement terms. After the charges are filed, Google will have 10 weeks to respond to the claims, and have the opportunity to call for a hearing to argue its case more fully, according to the Financial Times.
Update, 4:49 p.m. PT: Adds response reportedly from a Google internal memo.