BHP Billiton and Rio Tinto said they were disappointed with the German Federal Cartel Office's plan to prohibit their proposed US$116bn iron ore joint venture in Western Australia.

"The parties continue to believe that the joint venture is pro-competitive and will increase the supply of iron ore," the miners said in a statement on Thursday.

The German regulatory process is continuing and a formal notification is expected to be received by the miners next week.

"No decisions about next steps have been taken at this stage while regulatory discussions continue," the miners said.

Regulators in Australia, Japan, and other markets are also reviewing the deal, but analysts see the Commission as the biggest hurdle due to opposition from EU steel producers.

EU antitrust regulators will meet with Rio and BHP, the third-largest iron ore producer, by the end of this month to discuss the joint venture.