EU antitrust regulators fined Google parent Alphabet (GOOGL - Get Report) €1.49 billion ($1.7 billion) for unfairly restricting rivals from displaying ads on its platform via third parties using its AdSense tool.

The fine is the third in two years levied against Google and could increase tensions between Brussels and Washington as the two sides continue to hammer out a trade deal after suspending tariff increases in the summer of 2018. Regulators said Google abused its market dominance by restricting third-party websites, such as newspapers, blogs and travel aggregators, from placing ads from Google's rivals.

"Google has cemented its dominance in online search adverts and shielded itself from competitive pressure by imposing anti-competitive contractual restrictions on third-party websites," Competition Commissioner Margrethe Vestager said in a statement.  "This is illegal under EU antitrust rules. The misconduct lasted over 10 years and denied other companies the possibility to compete on the merits and to innovate - and consumers the benefits of competition."

Google shares slipped modestly lower in following the EU ruling to $1,201.10 each in the opening minutes of trading on Wall Street.

Last year, Google was fined a record $5 billion by European antitrust authorities following a lengthy investigation into contracts that tie makers of android-operated smartphones to the exclusive sale of its apps.

That decision followed a €2.4 billion levy from Brussels for denying "other companies the chance to compete on the merits and to innovate" in the market for price comparison searches on its website.

Vestager defended that decision Wednesday, telling reporters in Brussels that changes made by Google following that ruling have increased traffic for rivals and resulted in "positive developments."