Coca-Cola Co's quarterly results slightly missed Wall Street estimates, as the Japan earthquake and the timing of marketing expenses overshadowed strong sales volume, and its shares fell 2.3 percent.

In addition, the world's largest soft-drink maker saw less of a benefit than expected from price increases, and its margins suffered, according to UBS analyst Kaumil Gajrawala.

We characterize first-quarter results as slightly disappointing, given consistent 'beats' over the last few years, Gajrawala said.

He added that year-ago comparisons are also set to become more difficult as 2011 progresses, due to last year's World Cup, discounting at Wal-Mart, and generally warm weather.

We believe this could present a near-term challenge to Coca-Cola shares given the company's premium to the sector.

(For a graphic on Coca-Cola shares, see: http://r.reuters.com/sas29r)

Coke said on Tuesday net income rose to $1.9 billion, or 82 cents per share, in the first quarter, from $1.61 billion, or 69 cents per share, a year earlier.

Earnings per share were reduced by 1 cent because of lost revenue in Japan following the earthquake in March and 1 cent from the timing of marketing expenses as the company conforms its newly acquired bottling business to its accounting schedule.

Excluding those items, and restructuring and other charges, earnings were 86 cents per share, missing the average analyst estimate by a penny, according to Thomson Reuters I/B/E/S.

Net operating revenue rose 40 percent to $10.52 billion, in part because of last year's acquisition of North American bottling operations. Analysts on average were expecting $10.57 billion, according to Thomson Reuters I/B/E/S.

Worldwide volume rose 6 percent in the quarter, with North American volume, excluding new cross-licensed brands like Dr Pepper, up 2 percent.

Sales volume rose 7 percent in Latin America, 1 percent in Europe, 8 percent in Eurasia and Africa and 5 percent in the Pacific region.

Coke bought its North American bottling operations in October to streamline its distribution system and cut costs. PepsiCo Inc
, which bought its bottlers earlier in the year, will report quarterly results on Thursday.

Coca-Cola expects currency exchange rates to boost full-year operating income by a low- to mid-single-digit percent rate.

Through Monday, Coke shares gained 10 percent since mid-March, when a beverage industry newsletter reported that Diet Coke overtook Pepsi-Cola as the No. 2 soda in the United States last year behind Coca-Cola.

Still, weak consumer spending, rising oil and commodity inflation have weighed on soft drink makers.

Credit Suisse analyst Carlos Laboy said in a research note on Monday that Coke shares were trading at 15.8 times his 2012 earnings estimates, a 30 percent discount to their 10-year average multiple.

Coca Cola shares were down $1.55 at $66.19 on the New York Stock Exchange.

(Reporting by Martinne Geller, editing by Maureen Bavdek, Derek Caney and Robert MacMillan)