BRUSSELS (Reuters) - German car parts maker ZF Friedrichshafen [ZFF.UL] is set to win conditional European Union antitrust approval for its proposed $13.5 billion (8.8 billion pound) takeover of U.S. peer TRW Automotive Holdings Corp (>> TRW Automotive Holdings Corp.), two people with knowledge of the matter said on Wednesday.

ZF, which is seeking to bulk up and expand into the potentially lucrative self-driving car market, offered concessions to the European Commission last month in a bid to allay regulatory concerns.

"It's a conditional phase 1 approval," said one of the sources, referring to the Commission's preliminary review of the deal.

Neither the EU competition authority nor the companies disclosed details of the concessions.

ZF sold its steering systems business to German industrial group Robert Bosch [ROBG.UL] in September last year in an effort to clear potential antitrust hurdles.

Commission spokesman Ricardo Cardoso and a ZF spokesman declined to comment.

TRW said: "TRW will only provide updates to the extent that the anticipated timing of the transaction may change, but do not intend to provide interim updates for each step of the process."

The Commission has set a March 12 deadline for its decision.

ZF Friedrichshafen, which supplies chassis components to Audi (>> Audi AG), BMW (>> Bayerische Motoren Werke AG) and others, already helps carmakers develop hybrid-powered transmissions.

Self-driving cars and the technology to develop them has even attracted interest from Silicon Valley companies such as Google (>> Google Inc) and Apple (>> Apple Inc.), pitting them against the traditional carmakers.

TRW, which makes car safety products such as brakes and air bags, counts Ford (>> Ford Motor Company), General Motors (>> General Motors Company) and Volkswagen (>> Volkswagen AG) among its clients.

(Additional reporting by Ben Klayman in Detroit, Edward Taylor in Frankfurt and Ilona Wissenbach in Dusseldorf, editing by David Evans)

By Foo Yun Chee