Bolivian President Evo Morales says he is going to the international courts to demand access to the Pacific Ocean for his landlocked country.
He said talks with Chile had made no progress.
Bolivia lost its route to the sea in the War of the Pacific more than 130 years ago.
Chile’s President Sebastian Piñera said the move was a serious obstacle to relations.
Diplomatic ties between the two countries were severed in 1978.