Venezuela has signed agreements with international oil companies to take majority control of four oil fields along the Orinoco River.

Under the agreements, the oil companies will hand over operations at the sites on May 1 to Venezuela's state-owned oil company, PDVSA. The transfer is part of Venezuela's plan to nationalize the country's energy assets.

The agreements were signed Wednesday in Venezuela by officials from U.S. company Chevron Corporation, Britain's BP PLC., France's Total SA and Norway's Statoil ASA. U.S.-based ExxonMobil Corporation agreed to the handover earlier.

U.S.-based oil producer ConocoPhillips has refused to sign the agreements. The company has the largest stakes in the oil fields to be transferred to Venezuelan control.

Talks between ConocoPhillips and the Venezuelan government are continuing.

Some information for this report was provided by AP and Reuters.