BRUSSELS (Reuters) - European Union antitrust regulators have extended a deadline for a decision on Telefonica's (>> Telefonica SA) 8.6-billion-euro (7 billion pounds) bid for KPN's (>> KPN KON) German unit to June 26 after receiving additional data from the Spanish telecoms operator.

The move by the European Commission came after it halted its review of the deal last week while waiting for Europe's biggest telecoms firm by revenue to provide the details.

"Since Telefonica supplied the information requested, the clock has restarted on 8 May. The deadline for the Commission to take a decision in this investigation is now 26 June," said Antoine Colombani, Commission spokesman for competition policy.

Telefonica earlier this month sweetened its offer of concessions in a bid to allay regulatory concerns that the deal would reduce competition and lead to higher prices in Europe's biggest market.

Sources told Reuters the new elements include giving wi-fi hotspots to rivals and increasing the maximum capacity available to competitors on the merged company's network to 30 percent from 20 percent.

Separately, the Commission said it would decide by Sept. 19 and not Sept. 18 whether to clear U.S. cable company Liberty Global's (>> Liberty Global PLC) proposed takeover of Dutch peer Ziggo (>> ZIGGO).

The EU antitrust authority last week opened an in-depth investigation into the deal, concerned that it would reduce competition in the Dutch pay TV and telecoms markets.

(Reporting by Foo Yun Chee; editing by Jan Strupczewski)