Halliburton's (NYSE: HAL) plan to acquire Baker Hughes Inc. (NYSE: BHI) and create the world's biggest U.S. oilfield services provider faces more delay after European Union antitrust regulators halted their investigation into the $35 billion deal for the second time.

The European Commission said the companies have yet to provide an important piece of information.

"Once the missing information is supplied by the parties, the clock is re-started and the deadline for the Commission's decision is then adjusted accordingly," Commission spokesman Ricardo Cardoso said in an email.

The EU competition authority is concerned that the deal may reduce competition and innovation in more than 30 product markets, both onshore and offshore. It had suspended the deal review for about two weeks in February for a similar reason.

Halliburton, which is willing to divest businesses with combined 2013 revenue of $5.2 billion to sooth regulators, has yet to make a formal offer of concessions. The deal comes amid weak oil prices and reduced drilling activity.

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