The Deutsche Telekom unit is Austria's second-biggest mobile provider after Telekom Austria. Two smaller rivals - France Telecom SA's Orange and Hutchison's H3G - are trying to merge in a deal that is under regulatory review.

Bierwirth told WirtschaftsBlatt in an interview printed on Wednesday he was worried what would happen if H3G got LTE spectrum at the same time as a merger came through.

H3G and Telekom Austria's A1 would then, for two years, have an advantage by owning frequencies needed for Apple's popular iPhone 5 to use LTE, he said.

"That would be a massive skewing of competition," he added.

In such a case T-Mobile would need to review its market positioning.

"We would scale back investment plans massively," he said.

Asked if that meant T-Mobile could quit Austria, he said: "I wouldn't want to rule out any options for this case."

Austrian regulators denied a website report on Tuesday that European Union and domestic officials had already agreed to approve H3G's takeover of Orange Austria. "There is nothing to this," a spokesman for the Austrian competition authority said.

Hutchison 3G this month made more concessions in a bid to get clearance for its planned 1.3 billion euro ($1.7 billion)purchase of Orange Austria. The European Commission is set to decide on the case by December 21.

(Reporting by Michael Shields; Editing by Mark Potter)

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