* Interpublic expects FY organic rev growth of 1-2 pct
* Had earlier expected organic growth of 3-4 pct
* 3rd-qtr earnings, revenue miss estimates
* Shares down 6.5 pct; other ad firm stocks also fall (Adds ad industry background, CEO comment, updates share price)
Oct 24 (Reuters) - U.S. advertising company Interpublic Group slashed its annual forecast for organic revenue growth and reported disappointing third-quarter earnings on Tuesday, as many of its biggest clients cut back on spending.
Shares of Interpublic, one of the world's "Big Four" advertising groups, fell nearly 5 percent to $19.59 in morning trading.
Interpublic, like its peers, is under pressure to adapt to an industry transformed by Google and Facebook, which dominate online advertising - a channel that helps advertisers target consumers better.
Consulting firms such as Accenture and IBM have also taken market share away from traditional ad groups in recent years by expanding their marketing divisions through aggressive acquisitions.
"Organic revenue was negatively impacted by broader trends that are being felt throughout much of the industry," Interpublic Chief Executive Michael Roth said in a statement.
Shares of Interpublic's rival "Big Four" firms - Britain's WPP, France's Publicis and New York-based Omnicom - all fell 2 to 3 percent on Tuesday.
While Publicis's third-quarter sales missed market forecasts last week, hurt by fierce competition in online ads, WPP in August cut its sales target, as consumer goods giants curbed spending.
Omnicom, however, reported better-than-expected third-quarter revenue last week, benefiting from surprisingly strong demand in North America.
New York-based Interpublic, which counts Microsoft and Coca-Cola among its clients, now expects full-year organic revenue growth of 1 to 2 percent, down from the previously expected 3 to 4 percent range.
The company's third-quarter revenue and earnings fell short of analysts' estimates, led by a 1.3 percent decline in international revenue to $746.6 million.
Interpublic said revenue from the United States, which makes up more than 60 percent of total revenue, fell 0.8 pct.
The company saw a "significant" cutback in spending from consumer goods companies, Roth said on a call with analysts.
Analysts have raised concerns about ad agencies' exposure to the consumer goods industry, which is facing pressure from Amazon.com Inc and other technology platforms.
"Several of our largest clients continue to defer or cancel projects spending, which particularly weighed on the growth of our digital and marketing services disciplines," Roth added.
Interpublic's net income rose 13.7 percent to $146.2 million or 37 cents per share. Excluding one-time items, it earned 31 cents per share.
Total revenue dipped 1 percent to $1.9 billion.
Analysts had expected a profit of 33 cents per share and revenue of $1.96 billion, according to Thomson Reuters I/B/E/S. (Reporting by Arjun Panchadar and Aishwarya Venugopal in Bengaluru; Editing by Sai Sachin Ravikumar)