* Fourth-quarter adjusted earnings $1.18/share vs est. $1.16
* Fourth-quarter revenue rises 2.9 pct to $4.06 bln
* Omnicom shares gain as much as 2.5 pct (Adds merger details, background, executive comments)
By Aurindom Mukherjee
Feb 11 (Reuters) - Omnicom Group Inc, the largest U.S. advertising company, reported a better-than-estimated 2.9 percent rise in quarterly revenue due to growth in its international markets and said its merger with France's Publicis Groupe SA was taking longer than expected.
Omnicom announced a $35.1 billion merger with Publicis in July to create the world's biggest advertising agency.
The proposed merger is "highly complex" and is yet to receive clearance from China, Omnicom Chief Executive John Wren said on a conference call. "We received clearance from all other jurisdictions."
Omnicom said it now expected the deal to close "a little bit into the third quarter."
The company said in October that it expected the merger to close in early 2014.
The New York-based company, whose proposed merger with Publicis was cleared by EU regulators last month, reported a 4.3 percent rise in sales outside the United States, its biggest market.
Omnicom, which owns agencies such as BBDO Worldwide and Goodby, Silverstein & Partners, said sales rose 3.2 percent in the United States.
The company's net income was $300.5 million, or $1.13 per share, in the fourth quarter ended Dec. 31 compared with $307.1 million, or $1.13 per share, a year earlier.
Excluding merger expenses, Omnicom earned $1.18 per share.
Total revenue rose to $4.06 billion. Organic revenue from the company's Europe markets rose 2.6 percent.
Analysts on average had expected earnings of $1.16 per share on revenue of $4.03 billion, according to Thomson Reuters I/B/E/S.
Omnicom said the fourth-quarter results included a $13.3 million pre-tax charge related to the proposed merger with Publicis.
Omnicom's shares were up 0.6 percent at $74.63 on Tuesday morning on the New York Stock Exchange. The stock rose as much as 2.5 percent earlier. (Additional reporting by Supantha Mukherjee in Bangalore; Editing by Kirti Pandey)