EU regulators had identified "serious concerns" because the combined company, as a provider to travel agencies, would have market shares from 40 percent to over 70 percent in Belgium, Hungary, Ireland, Italy, the Netherlands and Britain.

They said they would investigate further how the deal would affect the market and make a decision to clear or block the deal by Sept. 13.

The Commission rarely prevents takeovers but it can, and often does, ask companies to sell off units or make promises to change their business behavior.

Travelport's Galileo system is second only to Amadeus. Buying Worldspan means the new business would have only two rivals ? Amadeus and the third-placed player Sabre.

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