Cuba expects to kick start its deepwater oil exploration activity with assistance from Angola's state-run energy company Sonangol, a Cuban official said.

Cuba is opening its doors more for Western powers after a long Cold War policy of isolation from the United States. The country in the past worked to cut the amount of oil it imports from Venezuela through development of its own offshore reserves.

An unnamed official from Cuba's Cubapetroleo, or Cupet, told energy reporting service Argus the preliminary deal with Sonangol outlines drilling schedules.

"The matters to be determined include which of the blocks contracted by Sonangol will be drilled, the sourcing of a rig and the timing of the start of the work," the official said.

The U.S. Geological Survey, which reviewed Cuba's offshore potential as the thaw began earlier this year, estimated there were about 4.6 billion barrels of crude oil and 9.8 trillion cubic feet of natural gas in the form of undiscovered, technically recoverable, reserves in Cuba. About three-quarters of that is said to be located within 50 miles from shore.

The United States and Cuba formally restored diplomatic relations earlier this week. Prior to the trade embargo enacted in 1962, U.S. companies held interests in several petroleum refineries in Cuba.

The Cupet official told Argus there was scant interest from U.S. energy companies despite invitations from Cuba.

"We want to ensure all is in place for interested companies if and when the United States lifts its damaging economic embargo on our country," the official said.

Venezuela dominates the sector by meeting more than 60 percent of the country's petroleum demand. The second largest refinery in Cuba processes only Venezuelan crude oil.