The EU announced that it is starting an investigation into the deal after Qualcomm failed to offer concessions to address antitrust commission concerns.

Qualcomm will become the leading supplier to the fast growing automotive chip market following the deal. However the EU has a list of concerns about the combined company's ability and incentives to squeeze out rivals and jack up prices.

It is worried that the company may bundle its products, excluding rivals in baseband chipsets and near field communication (NFC) chips.

The combined entity would have the ability and the incentive to change NXP's intellectual property licensing practices, in particular the NFC technology, by tying this to Qualcomm's patent portfolio, the EU watchdog said.

It voiced concerns about reduced competition in semiconductors used in cars. The Commission will decide on the deal by Oct. 17.

However, Qualcomm says it is confident it can allay the EU's worries and that it still expects to close the deal by the end of the year. The US antitrust enforcers gave the green light for the deal in April without demanding concessions.