BRUSSELS (Reuters) - EU antitrust regulators are seeking feedback on whether the European Energy Exchange (EEX) might expand its market power by bundling products when it buys Nasdaq's European power trading and clearing business, a person with direct knowledge of the matter said on Wednesday.

The European Commission, which is examining the deal, sent a questionnaire to the companies' rivals and customers this month, asking for replies early this week, the person said. EEX is Europe's leading electricity and natural gas exchange, serving 800 participants.

"One dedicated section in the questionnaire is about conglomerate effects," the person said, referring to the impact on competition from the merger of two companies in closely related but not competing markets.

"The Commission would like to understand whether the merged entity could use its strong position in one market to increase its market position in markets of similar products," the person said.

The questionnaire asked if the merged entity might do this by offering products only as part of bundles for a fixed fee or making the sale of one product conditional on the sale of another related one, the person said.

The Commission, which last year said the merged company could have an incentive to raise trading fees or worsen conditions for market participants, declined to comment.

The questionnaire also asked about the impact of the deal on prices and the barriers for rivals to enter the market, the person said.

EEX and Nasdaq in their response to the Commission last year said the deal posed no significant threat to competition in Denmark, Finland, Sweden, Norway or any other EU country, that it would not eliminate competition between the two companies, and that market reaction had been positive.