Bolivia has filed a lawsuit against Chile at the International Court of Justice in The Hague to reclaim access to the Pacific Ocean.
Bolivia lost access to the coastline in a 19th Century war with Chile, leaving it landlocked ever since.
Chile says Bolivia's demand has no historical or legal basis.
The BBC reports the two countries have had limited diplomatic relations since 1978. Previous attempts to negotiate the redrawing of the border have failed.
The borders between the two neighbours date back to the 1904 Treaty of Peace and Friendship, signed after Bolivia lost 400km of coastline to Chile during the War of the Pacific (1879-1884).
Bolivia has long tried to reclaim the territory. It still maintains a small navy and each year celebrates the Day of the Sea.
President Evo Morales announced his intention to take the case to the International Court of Justice at this year's celebrations to mark the day.
The Chilean government said it was not worried about the move.