Venezuela's state oil company says it wants to increase its share to 60 percent in four heavy oil projects in the Orinoco River basin.
A company director, Eulogio del Pino, who oversees contracts with foreign oil companies made the announcement Wednesday.
The projects are worth an estimated $33 billion. Venezuela now has a minority stake in partnership with foreign companies including U.S.- based Chevron, ExxonMobil and ConocoPhillips, and France's Total.
They are developing what Venezuela says are some of the largest untapped oil reserves in the world.
Venezuela is the world's fifth-largest oil exporter, and President Hugo Chavez has been taking measures to strengthen state control of the energy sector.
Mr. Chavez has accused foreign oil companies of exploiting his country's petroleum reserves without paying sufficient taxes. Some information for this report was provided by AP and Reuters.