Argentina and Brazil are Uruguay's most important trading partners: Argentina accounted for 20% of total imports in 2009. Since bilateral relations with Argentina are considered a priority, Uruguay denies clearance to British naval vessels bound for the Falkland Islands, and prevents them from calling in at Uruguayan territories and ports for supplies and fuel. A rivalry between the port of Montevideo and the port of Buenos Aires, dating back to the times of the Spanish Empire, has been described as a "port war". Officials of both countries emphasized the need to end this rivalry in the name of regional integration in 2010.