Norway's state-owned oil firm Petoro has previously signed deals to buy stakes amounting to 30 percent of the Norwegian Sea field from Austria's OMV and Denmark's Maersk Oil .

"The state may raise its stake further," the oil ministry said in a document published as part of Norway's fiscal budget process.

Operator DEA, controlled by Russian billionaire Mikhail Fridman, last month unveiled a 10 billion Norwegian crowns ($1.17 billion) development plan for the field.

DEA holds a 40 percent stake in the field and has agreed with Maersk to raise this to 50 percent. Italy's Edison owns the remaining 20 percent.

OMV and Maersk will no longer own stakes in Dvalin if the planned transactions are approved by regulators and by parliament.