Italians are voting in a referendum on the duration of offshore drilling concessions in territorial waters, as nine regional governments seek to wrestle some influence over energy policy away from the central government in Rome.

Premier Matteo Renzi says he will abstain from voting Sunday, sending a signal that could kill the vote that requires a quorum of 50 percent plus one to make the balloting valid.

The battle began when Renzi's government in December extended all existing 30-year concessions within 12 kilometers (7.5 miles) of shore until resource exhaustion. That angered regional governments, who were concerned about safety, the environment and pushing for a more renewable energy policy.

The amount of resources at stake is equal to 3 percent of Italy's annual domestic demand for gas and 1 percent of annual demand for oil.