Strike extended at key Argentine grain ports

Workers demand up to 100 percent pay hike

* CBOT soy price jumps on strike (Recasts, updates throughout)

BUENOS AIRES, March 29 (Reuters) - Argentina's biggest grains export complex came to a near standstill on Monday after dockworker strikes blocked access to most shipping terminals in San Martin and Timbues ports.

Soybean prices on the Chicago futures market soared on news of the strike, which comes just as the South American nation begins to harvest what is expected to be a bumper soy crop in the world's third biggest exporter of the grain and the world's top provider of soy derivatives such as soybean oil and meal.

In an extension of protests that began last week, workers striking over wages widened protests burned tires and prevented grain trucks from entering the two ports and others near Rosario, in Santa Fe province, 500 km (310 miles) north of Buenos Aires, union and media sources said.

"We are waiting for the terminals to call us and we'll surely sit down again for talks. Negotiations have not been cut off," Herme Juarez, president of the Port Workers Cooperative and the United Syndicate of Argentine Port Workers, or SUPA in Spanish, told Reuters.

The dockworkers are demanding wage hikes of up to 100 percent. Exporting companies have offered raises of 25 percent, with an additional raise of 15 percent next year, but so far have not come to an agreement with the workers cooperative.

"We have made a more than reasonable offer," an industry source told Reuters. The source said the strike is blocking more than 200,000 tonnes a day in exports and has already caused millions in losses.

The strike began last week and at first affected only two terminals at San Martin port, but had spread to at least seven of Rosario's 11 terminals by Monday.

The protests affected access to terminals belonging to Bunge (BG.N) and Aceitera General Deheza, Cargill [CARG.UL], Toepfer, Nidera, Dreyfus, Minera La Alumbrera and Noble, with only Buyatti's terminal remaining open.

The strike pushed U.S. soybean futures up for the second day, with CBOT prices rising sharply on Monday. [GRA/]

"It's a little early right now, their big export program hasn't started yet but if it continues it will have a big impact on the soybean market," said Jack Scoville, analyst for Chicago-based trade house The Price Futures Group.

Argentina's soy crop is expected to total between 51 million and 55 million tonnes, a sharp increase from 37 million tonnes last year when a drought hit production.

The stevedores union estimates that for each day of protests, they are blocking exports of 100,000 tonnes of grain, affecting $12.5 million in exports, according to la Nacion newspaper.

"It looks like strike season is on so that's going to be supporting the old-crop months (CBOT May and July soybean futures)," a CBOT trader said.

Although strikes are not unusual at the beginning of harvest season, they are usually short-lived. The last significant interruption to soy exports took place in 2008, when a strike by Argentinian farmers hit exports.

Some analysts feared that the lack of a quick resolution to the conflict could lead to an extended strike.

"If it is not settled before Easter, it could drag on a lot longer," said Mario Balletto, oilseeds analyst for Citigroup.

The strike comes as analysts put inflation estimates for Argentina in 2010 between 20 and 30 percent.