BRUSSELS (Reuters) - U.S. advertising company Omnicom Group Inc (>> Omnicom Group Inc.) and French peer Publicis Groupe SA (>> PUBLICIS GROUPE) have asked European Union antitrust regulators to approve their proposed $35.1 billion (21.7 billion pounds) merger to create the world number one agency.

Omnicom, the world's second biggest agency, and No. 3 Publicis unveiled the merger in July, saying it would help them compete better with online rivals.

The European Commission said it would decide by January 9 whether to clear the deal, according to a filing on its website on Tuesday.

Regulators in the United States, South Korea, Canada, India, Turkey and South Africa have already cleared the deal.

Omnicom's clients include PepsiCo (>> PepsiCo, Inc.), Apple Inc (>> Apple Inc.), Microsoft Corp (>> Microsoft Corporation) and AT&T (>> AT&T Inc.). Publicis has Coca-Cola (>> Coca-Cola Bottling Co. Consolidated), Verizon (>> Verizon Communications Inc.) and Google Inc (>> Google Inc).

Omnicom and Publicis compete with current leader WPP (>> WPP PLC), U.S.-based Interpublic (>> Interpublic Group of Companies Inc), France's Havas (>> HAVAS) and Japan's Dentsu (>> Dentsu Inc).

(Reporting by Foo Yun Chee; Editing by Louise Heavens)