* Q4 organic growth 3.9 pct, sales 1.9 bln euros
* Proposes dividend of 0.90 euros/share
* Europe to remain weak, U.S. recovery underway-CEO
* 2013 aim to "slightly improve" op margins-CEO
* Forecasts organic growth above 2012, better than market (Adds CEO comments, details)
By Leila Abboud and Catherine Monin
PARIS, Feb 14 (Reuters) - Ad agency Publicis finished 2012 on a high note as sales got a big bump from emerging markets and on-line marketing, yet it warned on Thursday that the year ahead would be difficult, especially in Europe.
The group, which competes with larger rivals WPP and Omnicom, posted organic growth of 3.9 percent in the fourth quarter, recovering from a sharp slowdown in advertising spending in September.
It reached 2.9 percent organic growth on sales of 6.61 billion euros ($8.88 billion) overall for the year, ahead of analysts' average expectations.
But Chief Executive Maurice Levy said that a year featuring the Olympic Games, European football championships and U.S. elections failed to spur big companies to boost global ad spending in the way forecasters and ad executives had hoped.
"The global advertising market had been expected to grow 4.7 percent, but actual growth fell below the 3 percent mark with advertising income from Euro 2012 and the London Olympics well below expectations," he said.
"While 2012 was more difficult than expected, 2013 looks like it will be even more difficult with Europe really remaining the problem child. There is, however, a renewal of consumer confidence in the U.S. as housing and equity markets strengthen, but the recovery remains fragile."
Levy did not give a growth target for the advertising market overall this year, but said Publicis would grow faster than the sector and outpace last year's 2.9 percent organic growth.
"Digital advertising is now our biggest source of revenue for the first time, bringing in 33 percent of sales and allowing us to succeed despite continued economic headwinds," said Levy.
Publicis' ZenithOptimedia forecasting unit predicted in December that global ad sales would rise 4.1 percent this year, but Publicis said that was "quite high" on Thursday.
Ad spending generally tracks economic growth, so slowdowns in world markets tend to have a knock-on effect for ad agencies. With the growing importance of on-line campaigns, big advertisers such as carmaker General Motors and electronics maker Samsung are constantly adjusting budgets instead of committing further ahead to TV or print ads.
Omnicom, which reported a forecast-beating fourth quarter on Tuesday, also cautioned that uncertainty in some markets and continued weak demand in Europe would pressure ad spending this year.
Despite macroeconomic uncertainty, Publicis said it aimed to "slightly improve" its operating profit margin this year.
In 2012, the group kept tight control on costs, especially on staff, to deliver on its target of stable margins of 16.1 percent compared with 16 percent in 2011.
Full-year operating profit rose 14 percent to 1.06 billion euros, while net income was 737 million. Analysts expected sales of 6.56 billion, operating profit of 1.17 billion and net income of 693 million.
Publicis also raised its dividend for 2012 to 0.90 euros per share after paying 0.70 per share last year. Levy reiterated the group's intention to increase its dividend payout ratio to 35 percent in the medium-term from 24.5 percent in 2012.
Even as it increases returns to shareholders, Levy said Publicis would continue to look for acquisitions to bolster its business in emerging markets and digital advertising. He added that the acquisition budget would likely remain on a par with the 454 million euros spent in 2012.
Publicis agreed to buy Dutch digital ad specialist LBi International in September in a 416 million-euro deal.
The advertising sector has been in a period of consolidation with Japan's Dentsu agreeing to acquire Britain's Aegis and big ad agencies like WPP and Publicis competing to snatch up digital agencies in China and Brazil. ($1 = 0.7442 euros) (Editing by James Regan)