BRUSSELS (Reuters) - Omnicom (>> Omnicom Group Inc.) and Publicis (>> PUBLICIS GROUPE) will win unconditional European Union regulatory approval for their $35.1 billion merger to create the world's biggest advertising agency, two people familiar with the matter said on Tuesday.

U.S. company Omnicom currently ranks second, behind WPP (>> WPP PLC), while Publicis is in third place. The deal will allow the combined company to better compete with online rivals in ad placement such as Google (>> Google Inc) and Facebook (>> Facebook Inc).

"The European Commission will clear the merger unconditionally," one of the people said. The EU competition authority has set a January 9 deadline for its decision.

"We are currently investigating and it would be very premature to speculate on the outcome of this investigation," said Antoine Colombani, Commission spokesman for competition policy.

Analysts had expected the deal to draw tough antitrust scrutiny because of the combined company's strong market share and possible concerns from major clients.

The French-U.S. giant would bring the accounts of major competitors in a number of industries such as Apple (>> Apple Inc.) and Samsung (>> Samsung Electronics Co., Ltd.), or Coca-Cola (>> The Coca-Cola Company) and PepsiCo (>> PepsiCo, Inc.), under one roof.

It will also group together Publicis agencies such as Saatchi & Saatchi and Leo Burnett with Omnicom's BBDO Worldwide and DDB Worldwide.

Regulators in the United States, South Korea, Canada, India, Turkey and South Africa have already nodded the merger through.

(Reporting by Foo Yun Chee; editing by John O'Donnell and Tom Pfeiffer)

By Foo Yun Chee