MOSCOW, July 6 (Reuters) – Russian Prime Minister Dmitry Medvedev has signed a decision imposing extra duties of 25-40 percent on some imports from the United States in response to Washington’s tariff move, the Russian economy ministry said on Friday. The extra duties will apply to imports of fiber optics, equipment for road construction, oil and gas industry, metal processing and mining, according to an economy ministry statement. Russia will impose duties on goods which have Russian-made substitutes, Economy Minister Maxim Oreshkin is quoted as saying in the statement.