Taiana met with activists in the Argentine provincial city of Gualeguaychu, where protesters sporadically blocked bridge access into Uruguay from December until just before Argentina filed a complaint with the World Court at The Hague in May.

Although Taiana's meeting may have been a move aimed at averting a return to roadblocks, the government's commitment to avoiding conflict while it pursues legal action is unclear.

Two weeks ago, the court rejected Argentina's request for a preliminary injunction that would have halted construction at the two pulp mill sites. The Hague ruling said Argentina could file future petitions with the court on merit, however.

"We came to reiterate the government's firm pledge to avoid contamination of the Uruguay River," Taiana said during a presentation to several hundred activists in a Gualeguaychu theater. Due to "their size, location, and technology, these pulp mills will cause irreparable damage for the region," he added.

Taiana also reiterated that the government will seek to discourage international lenders from funding the pulp mill projects.

Uruguayan officials have rejected the Argentine environmental claims, saying the plants will use the highest European environmental standards.

What's more, Uruguayan officials filed a complaint against Argentina with regional trade bloc Mercosur, alleging that the roadblocks cost the smaller nation some $300 million in losses and violated trade agreements.

Some observers say the Argentine government ignored the provincial environmental complaints until it was too late to avoid roadblocks.

Taiana's trip to Gualeguaychu, which included a pledge to incorporate two activist lawyers into the government's legal team, could have been a move to maintain calm in the area.

An Argentine legal filing Wednesday in Uruguay's Mercosur complaint clouds that outlook, however.

On Wednesday, the Argentine government defended the roadblocks as an expression of free speech, a move that could be interpreted as a nod for protesters to return to the bridge barricades. In any event, it was an ambiguous move for an administration averse to sending in police to restore order.

Streets in Buenos Aires are frequently blocked by various protesters, including club-wielding "piqueteros" who mask their faces with bandanas.

Of the two pulp plants, the larger is being built by Finnish consortium Metsa-Botnia Oy, which is owned by M-Real Oyj (MRLBV.HE), UPM-Kymmene Oyj (UPM) and Metsalitto. The second, which isn't as far along along, is being built by Spain's Grupo Empresarial ENCE SA (ENC.MC).

The two plants represent around $1.8 billion in total investment, and their output is expected to boost Uruguay's gross domestic product by a full 10%.