"We have agreed that the best U.S. instructors will finally start training the Ukrainian special forces, our special-operations troops, starting from November," Poroshenko told representatives of the U.S. Ukrainian diaspora after arriving in New York.

Foreign military instructors are already training units of the Ukrainian National Guard, he said. "This is mutual exchange, mutual assistance. This is interesting not only to Ukrainians, to learn from American partners how to fight. This is interesting to Americans, to learn how to beat Russia," said the Ukrainian head of state.

The training is part of U.S. efforts to strengthen Ukraine's security following Russia's seizure of the Crimea last year and the spread of separatist unrest in eastern, Russian-speaking regions of Ukraine.

Since few weeks, U.S. troops started training regular Ukrainian military forces later this year in an expansion of their current mission, which so far has been limited to instructing Interior Ministry national guard units.

U.S. Marines could deploy to the Eastern European country to train the Ukrainian naval infantry, said Capt. Richard Ulsh, a spokesman for Marine Corps Forces Europe and Africa.