Oil may be the commodity that reopens trade between the US and Cuba after a 46-year embargo that not even Americans' love of Havana cigars has been able to crack.

Cuba plans to begin drilling a major oil field off its northern coast next year and that may drive the two enemies together out of mutual interest.

"The sands are running out of the clock on the policy and I think that has the proembargo folks worried," said Sarah Stephens, director of the Center for Democracy in the Americas.

There was already a glimmer of hope that Fidel Castro's handover of the Presidency to his brother Raul in February may hasten a thaw.

The Cuban field holds at least five billion barrels of recoverable oil and 10 trillon cubic feet of natural gas, according to the US Geographical Survey and Cuba could be producing 525,000 barrels of oil a day within a few years.

The Havana government has sold oil concessions to seven companies. A team of Spanish, Indian and Norwegian firms begin drilling next year.