* Half of Rosario's soy-processing capacity hurt
* Agreement could be reached today - union leader
* Argentina is world's top soyoil, meal supplier (Adds talks continue without deal)
By Eduardo Garcia and Maximilian Heath
BUENOS AIRES, Dec 22 A strike by soy-processing workers in Argentina's biggest grains port halted at least six plants on Wednesday, disrupting crushing in the world's No. 1 soyoil and meal exporter and helping lift U.S. soyoil futures.
Crushing plants in and around the city of Rosario account for about 80 percent of Argentine soybean oil and meal output and the one-day-old pay strike is hitting plants owned by major exporters such as Cargill, Louis Dreyfus and Bunge .
Union and industry sources in Rosario said half of the area's soy-processing capacity was being affected by the strike, but some plants continued operating because not all workers belong to the union that is protesting for bonuses.
One union leader said a deal was possible to end the dispute quickly.
"I think we could reach an agreement today," union leader Daniel Succi told Reuters before entering talks with government officials and company representatives.
However, the negotiations continued late into the night without a quick breakthrough.
Six plants came to a halt after members of the San Lorenzo branch of the soy-crushing workers' union downed tools at midday on Tuesday, while four others were having trouble receiving soybean supplies due to pickets, the sources said.
If the strike is resolved quickly, exports to key markets including China, India and the European Union may not be affected.
But stocks of soyoil and soymeal in Rosario ports could start to run out as soon as Thursday, said a source at one export terminal, asking not to be named.
Another source at a leading grains exporter said stocks of soy products are traditionally low at this time of the year, and that relatively few shipments are due to be made.
Reaction to the strike at the Chicago Board of Trade was relatively muted, with all eyes focused on dry weather in the South American country, but the strike underpinned soy product values and helped keep a floor below soybeans. [ID:nNL3E6NM02]
The crushing workers' strike, called to demand a year-end bonus of 5,000 pesos ($1,227), is also hurting production at plants owned by Argentine companies Molinos Rio de la Plata and Vicentin. For a factbox see: [ID:nN2276658]
A spokesman for the CIARA-CEC chamber of soy-crushing companies was not immediately available for comment on the protest, which comes only weeks after a one-day protest briefly halted operations at plants in Rosario. [ID:nN06229236]
Pay-related strikes could become more frequent early next year as union leaders and company bosses prepare for wage talks in March or April. Annual inflation is privately estimated at between 25 percent and 30 percent in Argentina.
Argentina is the world's No. 3 soybean exporter after the United States and Brazil and its farmers produced a record 52.7 million tonnes in the last crop year, according to the Agriculture Ministry.
They are currently planting 2010/11 soybeans, but the impact of dryness linked to La Nina is raising concerns that production could be hit. ($1 = 4.075 Argentine pesos ) (Additional reporting by Nicolas Misculin, Helen Popper and Samuel Nelson in Chicago; Editing by Himani Sarkar)