By Saliou Samb

CONAKRY, Jan 3 (Reuters) - Guinea's two most powerful unions called on Wednesday for an indefinite general strike from next week to protest against the increasingly erratic rule of ageing President Lansana Conte.

Previous nationwide strikes have been over the price of basic goods and fuel, triggering widespread rioting and bringing the West African country to a standstill, but the latest planned action appeared to be the most overtly political yet.

The unions said the stoppage, called across the whole country from Jan. 10, was to denounce Conte's "repeated violations" of the country's basic laws and would continue until the rule of law was restored.

"We're putting on the table all the demands both of our supporters and of the population at large," Ousmane Souare, one of the main union negotiators, told Reuters.

"We've gone beyond the limit of what is acceptable."

Union leaders cited Conte's personal intervention last month to release one of his former allies, who had been arrested in a corruption probe, as well as the constant reshuffling of his cabinet which they said undermined his credibility.

There was no immediate reaction from the government, whose officials were unavailable for comment.

Guinea is the world's top exporter of bauxite, the raw material for aluminium, but most of its people live in poverty.

A stumbling economy, rampant corruption and powerful but fractious military have raised fears of instability in a country once seen as a bulwark against wars in neighbouring Sierra Leone, Liberia and Ivory Coast.

The deteriorating health of Conte, a reclusive diabetic in his 70s who seized power in a 1984 coup, has heightened nerves, raising the prospect of a dangerous power vacuum in the former French colony as rival factions compete to succeed him.

He personally secured the release of former ally and Guinea's richest man, Mamadou Sylla, in December along with a former central bank deputy governor, an act which the unions said rode roughshod over state institutions.

Last week he revised a cabinet reshuffle apparently under pressure from one of the rival political cliques vying to succeed him, presidency sources said. It was the second time in 2006 he had abruptly overturned his own cabinet reshuffle.

"There is no longer a State. You have the impression that when he signs certain documents he is not completely lucid. It's a scandal," opposition spokesman Mamadou Ba said. "It's shaming for our country."