FRANKFURT/BRUSSELS (Reuters) – EU antitrust regulators will open an in-depth probe into Telefonicas proposed 8.6 billion euro ($11.9 billion) takeover of KPNs German unit next week, three people familiar with the matter said on Thursday. The European Commision will reject a German request to take over examination a deal that will reduce the number of mobile telecoms operators in Europes biggest market from four to three, they added. Telefonica announced the deal in July, which will broadly put it on an equal footing with market leaders Deutsche Telekom and Vodafone. The EU competition regulator originally set a December 6 deadline for its preliminary review of the deal, but extended that to December 20 to consider a request from the Bundeskartellamt to take over the case.