The activists said they will take action Monday to protest the paper mill being built by Finnish company Botnia inside Uruguay near the river separating it from Argentina.

The project has been under dispute for months over concerns it will cause significant water pollution and devastate livelihoods along waterways in the area.

Argentina has taken the case before World Court in The Hague, and in early November Spain's King Juan Carlos offered to mediate the dispute.

But Argentine President Nestor Kirchner has asked the World Bank to delay its decision on financing the project, expected Tuesday, until the World Court announces its ruling.

Protesters voted Sunday to block an access road to General San Martin bridge crossing the Uruguay River that they say will be polluted by the mill.

The roads and bridges over the river, which forms the border between the two countries, have been the scenes of demonstrations and blockades for months by determined environmentalists and locals.

"At 2:00 pm (1700 GMT) we will begin a roadblock that will continue indefinitely," on Route 136, said Andres Rivera, leader of the Environmental Assembly of Citizens of Gualeguaychu.

Hundreds of protesters on Sunday marched on the site of the proposed mill in Uruguay.

"We want to show the World Bank that we are still on the march and that we are more than just 100 people opposed to Botnia," Gustavo Rivollier, a civic leader of Gualeguaychu, a town close to the proposed building site, told reporters on Sunday.

Rivollier branded as "false" World Bank reports that they had consulted with Gualeguaychu residents and had their approval for the project.

"They never came," he said.

The World Bank is expected to approve the loan package for Botnia -- a 170 million-dollar loan and 350 million dollars in credit guarantees, Argentina's Deputy Foreign Minister for Environmental Issues Estrada Oyuela told reporters on Sunday.

Nevertheless, he added, Buenos Aires is seeking to "avoid a friction point between Argentina and Uruguay that could last 50 or 80 years," referring to Kirchner's letter to the World Bank.

Argentina has also argued that the Botnia project should be put on hold until local populations around the site issue a so-called "social license" allowing the construction.

Buenos Aires says that Uruguay has violated a 1975 treaty about the use of the Uruguay River by authorizing the Botnia project and the construction of another paper mill in 2003.

Uruguay, for its part, is trying to keep the construction project on track and has gone before a Mercosur tribunal blaming the Kirchner administration for the persistent road blocks thrown up at three bridges over the river.

Mercosur is a South American free-trade area comprising Brazil, Argentina, Uruguay, Paraguay and Venezuela.

King Juan Carlos' envoy, Juan Antonio Yanez, offered to "facilitate" dialogue during a visit to Buenos Aires and Montevideo.

"We do not see any possibility of conciliation or mediation or dialogue," said Economy Minister Danilo Astori on Friday in Washington.

Uruguayan President Tabare Vazquez has officials lobbying the World Bank.