Venezuela will hold bidding rounds open to private companies for three blocks of the Orinoco heavy oil belt, Venezuelan state oil giant PDVSA said in a statement late on Thursday. Venezuelan Energy Minister Rafael Ramirez earlier this year said the government would bid out one block in the vast heavy oil reserve, following President Hugo Chavez's 2007 broad energy sector nationalization campaign. 'Soon there will be an announcement of the time frame to offer private, national and international companies three blocks in the Orinoco heavy crude belt, specifically (blocks) Carabobo I, Carabobo II and Carabobo III,' said the statement. Venezuelan law requires that PDVSA hold a majority stake in all upstream oil venture.