FILE PHOTO: The logo of German telecommunications giant Deutsche Telekom AG is seen at the company's headquarters in Bonn February 25, 2016. REUTERS/Wolfgang Rattay/File Photo

FRANKFURT (Reuters) - Deutsche Telekom DTEGn.DE has filed a lawsuit against Germany's Federal Network Agency protesting preconditions for participating in a next-generation mobile network frequency auction, Die Welt newspaper said on Tuesday.

Germany stipulated that bidders for 5G mobile frequencies must invest to expand the country’s mobile network and potentially allow new entrants to use their infrastructure.

The network regulator set a Jan. 25 deadline for auction submissions, saying the sale would begin in early 2019, but revised the preconditions for participation, drawing protests from the country’s main network operators.

Under the revised rules, a new market entrant without its own developed network, such as United Internet UTDI.DE, could bid for a 5G licence.

Deutsche Telekom’s suit claims the new preconditions call into question its investments and discourage further development of network infrastructure, particularly in rural areas, the German paper said, citing a Deutsche Telekom spokesman.

Deutsche Telekom could not immediately be contacted by Reuters.

Germany's three main network operators - Deutsche TelekomDTEGn.DE, Vodafone VOD.L and Telefonica DeutschlandO2Dn.DE - have now all sued the network agency seeking to determine the legality of the new preconditions. Deutsche Telekom, in which Germany holds a 31.9 percent stake, filed a suit against the Federal Network Agency with an administrative court in Cologne, Germany, Die Welt said.