By Peppi Kiviniemi Of DOW JONES NEWSWIRES BRUSSELS (Dow Jones)--The planned joint venture between Australian iron ore miners BHP Billiton PLC (BHP) and Rio Tinto Ltd. (RTP) faces prolonged antitrust scrutiny in Australia and Europe. Both the German Cartel Office and the Australian Competition and Consumer Commission said Monday they had extended their scrutiny of the mining giants' proposal to combine their iron-ore operations in the Pilbara region of Western Australia. The German cartel Office now aims to decide by Oct. 31 whether or not to clear the joint venture. "We need more time to analyze the relevant markets," Germany's Bundeskartellamt spokesman Kay Weidner said. The Australian authorities will meanwhile review the joint venture by July 22, due to having only received all the necessary information from the companies in early June. The European Commission, which is also probing the joint venture, said it would not comment on deadlines, adding only that its "investigation continues." But Amelia Torres, a spokeswoman for the commission's competition arm, said the commission is in "close touch with the German Cartel office." People familiar with the deal said it was unlikely the commission would reach a decision on the joint venture much before its German counterparts. The main reason for the deadline delay was due to the companies taking a long time to provide the antitrust authorities with all the necessary documents, a person familiar with the matter said. Clearance from the European Union's competition regulator is seen as the biggest potential hurdle to the joint venture, which failed in its initial form in 2008. The commission opened its antitrust investigation into the deal in January, citing concerns that the deal might have harmful effects on price competition in the worldwide market for iron ore transported by sea. Rio Tinto and BHP Billiton are, respectively, the second- and third-largest producers of iron ore in the world, after Brazil's Vale SA, the commission said. -By Peppi Kiviniemi, Dow Jones Newswires; +3227411483; [email protected] (Alex Wilson in Melbourne and Martin Rapp in Frankfurt contributed to this article) (END) Dow Jones Newswires June 21, 2010 06:05 ET (10:05 GMT)