UPDATE 1-Argentine grains buyers hoard as strike fears grow

(Adds farmers receiving court summons over supply law, quotes, byline)

By Nicolas Misculin

BUENOS AIRES, April 23 (Reuters) - Argentina's grains and livestock markets did brisk trade on Wednesday as buyers stocked up due to growing fears about farmers resuming a strike that caused beef shortages and hit exports, traders said.

Argentina's vast agricultural sector staged a three-week strike over a tax hike on soy exports in March, but farm groups agreed to suspend the protest and spend April in talks with the government.

However, farmers say the discussions are making little progress and some have warned they could break the 30-day truce if their demands are not met at the negotiating table, causing jitters in Argentina's grains and financial markets.

"We haven't advanced as much as we should have advanced," said Luciano Miguens, president of the Argentine Rural Society (SRA). "We're doing everything possible to arrive at May 2 with a firm proposal reached by consensus."

Soy prices held steady in the main grains port of Rosario, despite losses in the influential Chicago market, while prices rose in the main cattle market of Liniers. Strong demand drove both markets, traders and analysts said.

"Demand's pretty active today. The market's trying to anticipate a future strike that could start in 15 days," said Lorena D'Angelo, an analyst at the Rosario Grains Exchange.

"Both (oilseed) crushers and exporters are very active. The ports are full of trucks too," he added.

A day earlier, trade volume in Rosario was a heavy 70,000 to 80,000 tonnes. Volume fell back on Wednesday because farmers are holding out for even higher prices, traders said.

At Liniers, demand from meatpackers and supermarkets saw livestock prices rise. "Buyers sought to build up stocks for export amid concern the farm strike could return," one broker said.

In a step that could raise tensions further, farm leaders said they had received a court summons after Domestic Commerce Secretary Guillermo Moreno made a complaint under the controversial 1974 supply law, which is meant to curtail price speculation and guarantee supplies of basic goods.

Moreno, the government's price watchdog, is unpopular among farmers, who have accused him of using threats and pressure to influence the talks.

"There are people who want to put a spanner in the works. Today, we've received what we call a political pressure," said Mario Llambias, president of the CRA agricultural association, referring to the supply law summons.

The Domestic Commerce Secretariat has repeatedly used the supply law to fine energy companies over diesel shortages.

On the foreign exchange market, the peso currency ARSB= sank to its lowest level since early 2003 as investors snapped up dollars to protect themselves from the growing uncertainty over the negotiations. (Additional reporting and writing by Helen Popper; Editing by Braden Reddall)