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.