Busti argued the mills violated a treaty between Argentina and Uruguay allowing both countries to administer the Uruguay River.

"It will now be up to the international courts," Busti said, adding the petition could be submitted as early as next week.

The legal maneuvering is the latest by the governor to try to stymie the construction plans of the mills, scheduled to be built on the banks of the river that forms a natural border between the two countries.

Entre Rios province is located across the river from the planned site.

On the Argentine side, widespread opposition to the pulp mills has led to months of protests by environmentalists and ordinary Argentines who worry the plants will contaminate the region's farmlands, damage wildlife and choke off tourism.

Uruguayan President Tabare Vazquez has hailed the project -- among the country's largest foreign investment plans in history -- as crucial to its economy, now rebounding from a 2002 economic crisis.

The mills would be built by Finland's Metsa-Botnia, Europe's second-largest pulp producer, and Spain's Ence and are expected to produce 1.5 million metric tons of wood pulp for export.