BUENOS AIRES, Sept 6 (Reuters) - Mexico's Pemex disagrees with Spanish energy company Repsol's strategy of suing firms that partner with Argentina's state-owned YPF, said a board member of the Mexican state oil monopoly which holds a 9 percent stake in Repsol.
Argentina seized Repsol's majority stake in Buenos Aires-based energy firm YPF last year, arguing it had not done enough to invest in output.
Since then Repsol has vowed to sue any firm that partners with YPF, to cover losses stemming from the expropriation which it says merits a $10.5 billion reimbursement.
"We do not agree with the official position that Repsol adopted," Pemex board member Fluvio Ruiz said at an event in Buenos Aires on Friday.
"States have all the right in the world to decide the public policies that are best for their countries," Ruiz added.
His comments underscore tensions between Repsol and some shareholders as YPF seeks partners in Argentina's massive Vaca Muerta shale oil and gas deposits, one of the biggest unconventional reserves in the Western Hemisphere and an attractive prospect for global firms.
Ruiz said Pemex is talking informally with YPF about participating in the Vaca Muerta venture in the future.
Argentina finalized a $1.24 billion deal with U.S. oil company Chevron Corp in July to jointly develop Vaca Muerta, a partnership that Repsol has tried to thwart with a lawsuit.
In June, Pemex presented a $5 billion non-cash compensation proposal to Repsol on behalf of Argentina, which the firm's board rejected.
Argentina's government emphasized the proposal was not official.
"Pemex presented a proposal that it had worked out with the Argentine government, but it was not accepted by Repsol's board," Ruiz said.
Mexico nationalized the assets of foreign oil companies in 1938 to create the Pemex monopoly.
"It would be wrong of the board members of a company that emerged from a nationalization to question Argentina's authority," he said.