HUELVA, May 25 (RIA Novosti) - Fifteen Russian sailors arrested last year in Spain on drug trafficking charges pleaded guilty on Monday in exchange for a reduced three-year prison term, a defense lawyer said.

The lawyer said the sailors will have to pay a fine, and that if they fail to do so their terms will be increased by 30 days.

The court's final verdict is expected in a month's time, and lawyers intend to push for the sailors' extradition to Russia.

The sailors were detained on May 14, 2008 near the city of Huelva on southwest Spain's Atlantic coast in a large-scale police operation, after around four metric tons of marijuana was seized from their two vessels, both of which belonged to a Russian company.

A total of 34 people are implicated in the case, including Ukrainians, Romanians, Moroccans, Spaniards and Poles.