Repsol SA (REP.MC) will sue an Argentine company for signing a deal to develop shale oil and gas resources with its nationalized local unit YPF SA (YPF, YPFD.BA), a spokesman for the Spanish oil company said Friday. The spokesman said Repsol told Bridas International SA in a letter sent Jan. 2 that the Spanish firm would sue it for unlawful competition under Spanish law for partnering with YPF
Repsol SA (REP.MC) will sue an Argentine company for signing a deal to develop shale oil and gas resources with its nationalized local unit YPF SA (YPF, YPFD.BA), a spokesman for the Spanish oil company said Friday.

The spokesman said Repsol told Bridas International SA in a letter sent Jan. 2 that the Spanish firm would sue it for unlawful competition under Spanish law for partnering with YPF.

In May, Argentina's government nationalized a majority stake in YPF, the country's leading oil-and-gas company, after seizing its headquarters in Buenos Aires the previous month. Since then Repsol's YPF ownership declined to about 12% from more than 50%.

Repsol had said it would take legal action against any company that joins forces with YPF. Bridas signed such a deal late last year. Repsol has already sued to block international oil major Chevron Corp.'s (CVX) recent partnership with YPF.

Repsol has also filed a complaint against Argentina before the World Bank's arbitration center over the YPF nationalization.