Uruguay, in a major concession to Buenos Aires, said it will go slow on commissioning a second pulp mill on the river it shares with Argentina.

Uruguayan President Jose Mujica said he has no intention of irritating Argentina over the issue and would rather delay the second pulp million's commissioning than risk annoying Argentine President Cristina Fernandez.

"We know very well that if you try to push Argentina, you're done," Mujica said.

Worse still, he added, a quarrel with Argentina over pulp production would mean "you won't even get a thing of what you were planning for."

Argentina and Uruguay have been quarreling for several years over Uruguay's exploitation of its excess eucalyptus growth to turn into lucrative pulp for export. Finland's Botnia is Uruguay's partner in the specialized field of turning eucalyptus into a lucrative export commodity.

Argentina has opposed the pulp processing and took Uruguay to court over the first pulp mill on the Uruguay River. Neither environmental advocacy groups nor the International Court of Justice in the Netherlands could see anything wrong with the pulping process, but Buenos Aires warned it won't have any of it.

Argentina spent several million dollars on the lawsuit and eventually came around to Uruguay's point of view, in line with international legal opinion. But that didn't stop the country from continuing to raise objections over the pulping project.

Argentine Foreign Minister Hector Timerman said it was "perfectly known" that increased pulp production in Uruguay would raise the risk of river water contamination. He said an expansion would contravene a bilateral treaty reached after the resolution of a dispute over the first pulp plant.

He blamed plant operators for putting pressure on both Argentina and Uruguay through its actions.

"The Argentine government is addressing the issue too mildly," said Martin Alard, one of the leaders of the group which organized pickets that closed a Uruguay River bridge linking Argentina with Uruguay for several years before Buenos Aires intervened to stop the protest in 2010.

The protesters say the area is full of sulfur leaks from the plant and the water is contaminated. There has been no independent confirmation of that accusation and no recorded evidence of the eucalyptus pulping causing pollution in the shared Uruguay river.

Uruguayans say they don't want to annoy Argentina by confronting Fernandez with the lack of evidence of pollution. Argentina says the impact of the pollution taking place will be felt over a longer period.