The Spanish major is still smarting over the expropriation last year by the Argentine government of a majority stake in YPF, over which it claims it is owed over $10 billion and no compensation agreement has been reached.

"Repsol regret that a company like Chevron, that seeks endorsement from international community in its conflict with foreign states, is willing to take advantage from an illegal act entering into an agreement over the expropriated assets prior to the payment of a fair compensation to Repsol," chief financial officer Miguel Martinez San Martin said in a second-quarter earnings conference call with analysts, according to a Seeking Alpha transcript.

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