By Felipe Iturrieta
SANTIAGO, March 28 (Reuters) - South American neighbors Chile and Bolivia, which have long had thorny relations, are at loggerheads again - this time over access to a river that crosses their shared border.
Over the Easter weekend, Bolivian leftist President Evo Morales threatened to go to the International Court of Justice in the Hague to resolve a long-running but until now low-profile dispute over the river Silala.
Morales, who has been under pressure at home over an unfolding scandal involving a former girlfriend, argues that Chile has no right to use the water of the river, which originates in Bolivian territory and then flows into Chile.
But top copper exporter Chile, which uses some of the water in the parched Atacama desert to feed mine operations, says the waters are international.
Center-left President Michelle Bachelet said on Monday that Chile would counter with its own case in the Hague if Bolivia went ahead with its threat.
"We will carry out all necessary actions to protect our national sovereignty," she said.
Bolivia is already pressing a case against Chile in the Hague, seeking to force its neighbor to enter negotiations to grant it a corridor to the Pacific Ocean.
(Reporting by Felipe Iturrieta; Writing by Rosalba O'Brien; Editing by W Simon)