* Briceno suspended by ruling Socialist Party
* Says he was "sacrificed" for speaking out over oil leak
* Has been sparring with Chavez ally Cabello
By Andrew Cawthorne
CARACAS, March 20 (Reuters) - A Venezuelan state governor suspended from Hugo Chavez's ruling party for dissent said on Tuesday he was the victim of a cover-up over an oil spill and a vendetta by the president's most powerful aide.
Monagas state governor Jose Gregorio Briceno - better-known to Venezuelans by his nickname "The Cat" - was accused of repeatedly disobeying his superiors in the Socialist Party and was suspended last week pending an investigation.
The affair has highlighted power struggles in an election year amid uncertainty about Chavez's treatment for cancer. It has also thrown attention on several oil spills that the authorities have played down, despite widespread public concern.
Briceno had long sparred with Diosdado Cabello, the head of Congress and No. 2 after Chavez in the party who has this year returned to prominence as the president's most influential ally.
The final straw, however , seemed to be Briceno's refusal to toe the central government's line that the water in Monagas was safe for public consumption despite an oil leak into a local river.
After the party sanctioned him, Chavez rounded on Briceno in a speech on the weekend - as he did previously with another governor, Lara state's Henri Falcon, who broke with him in 2010.
"The governor of Monagas is a traitor to the people and will be turned into cosmic dust. He is going to disappear," the president said in an attack that was extraordinary even by his standards of bellicose rhetoric.
Replying in a letter to local media, Briceno said he had paid the price for sounding the alarm over last month's oil spill in the Guarapiche river, and for Cabello's desire to increase his influence in the Congress chief's home state.
"Just 24 hours after the start of the leak, with significant quantities of oil still pouring into the Guarapiche, senior officials asked me to open the water plants ... Of course, I did not accept this because it was too risky," Briceno wrote.
Socialist Party officials have denied he was suspended for his comments over the oil leak, and instead blame what they say were repeated acts of disobedience in local government matters.
Briceno , whose nickname echoes the initials of a political movement he launched years ago, said he felt forced to speak out in public about the spill.
"For breaking silence, I was finally sacrificed in the party with the vain argument of lack of revolutionary discipline ... How sad," he said.
"How could I do such an irresponsible and criminal thing as open the water taps with traces of oil? My dear God!"
The governor has big support within the eastern, oil-producing state of Monagas. There is speculation he may throw his support behind opposition candidate Henrique Capriles, who is challenging Chavez in the Oct. 7 presidential election.
Analysts, however, said that would be unlikely to change the equation much. Chavez is well ahead in the latest opinion polls, even though he is struggling with cancer.
Briceno was blistering about the role of Cabello, a former military comrade of Chavez who was president for a day in 2002 and helped to bring his boss back to power after a short coup.
"I have no doubt that behind this conspiratorial crusade against me is the legislator Diosdado Cabello," he said.
"With unchecked ambition and at whatever price, he wants to get his tentacles into the biggest oil-producing state in the country as well as please family members' appetite for seeing a Cabello in the Monagas seat of government."
Cabello has denied any personal motives.
As well as in Monagas, local officials say there have also been damaging oil spills this year in Zulia and Anzoategui states. State oil company PDVSA has said everything is under control, and one senior company executive even drank a glass of water straight from one of the rivers to show it was safe.
Chavez officials accuse opponents of exaggerating the impact of the leaks to discredit his government. Local media, however, have published pictures of oil-streaked rivers and quoted locals complaining about contaminated water and damaged wildlife. (Additional reporting by Deisy Buitrago; Editing by Daniel Wallis and Jackie Frank)