UPDATE 1-Norway's salmon producers eye U.S. as tariff falls

* U.S. trade officials drop 24 pct "anti-dumping" duty

* Norwegian salmon to remain niche product in U.S. - analyst

* American sushi eaters may start to see it - Marine Harvest (Adds detail, background, quotes)

By Walter Gibbs

OSLO, Jan 27 (Reuters) - Norwegian salmon farmers can freely send fish to the United States for the first time in 21 years after U.S. officials dropped a penalty tariff stemming from old charges that Norway had dumped underpriced salmon in U.S. markets.

Norway is the largest producer of farmed Atlantic salmon in the world and exported more than $5 billion worth last year, two thirds of it to other European countries.

The decision to rescind the 24 percent penalty duty on fresh whole Norwegian fish was announced on Thursday by the United States International Trade Commission.

"This gives us absolutely an extra opportunity," Alf-Helge Aarskog, chief executive of Norway's Marine Harvest ASA , told Reuters. "Norwegian salmon is attractive in the USA, and always has been."

The cost of air transport across the Atlantic will however keep Norway-based salmon farmers at a disadvantage to Canadian and Chilean competitors, analysts said, noting salmon was a globally priced commodity.