Chevron, the world’s third biggest oil company, said it had filed an international arbitration claim against the government of Ecuador, citing violations of the country’s obligations under the US-Ecuador bilateral investment treaty, investment agreements and international law.

The claim stems from what Chevron calls Ecuador’s “exploitation” of a lawsuit filed against Chevron, which accuses Texaco, which Chevron bought in 2001, of leaving an environmental disaster upon withdrawing from Ecuador in 1992.