Javier Galeano, Associated Press
An oil rig floats in the distance as fishermen work in Havana Bay, Cuba, Thursday Jan. 19, 2012. The Chinese-built oil rig arrived to Cuba to start exploratory drilling beneath the waters off Cuba's northern coast. Cuban leaders hope the rig will bring riches to a Communist country that is sorely in need of an economic boost. Spanish company Repsol is carrying out the exploratory effort under a contract with the Cuban government.

HAVANA — A massive drilling rig arrived Thursday in the warm Gulf waters north of Havana, where it will sink an exploratory well deep into the seabed, launching Cuba's dreams of striking it rich with offshore oil.

The Scarabeo-9 platform was visible from Havana's sea wall, far off on the hazy horizon as it chugged westward toward its final drill site, which lies about 30 miles (50 kilometers) north of Havana and 56 miles (90 kilometers) south of Key West.

Spanish oil company Repsol RPF, which is leasing the rig from Eni subsidiary Siapem for about a half-million dollars a day, said it expects to begin drilling within days to find out whether the reserves are as rich as predicted.

"The geologists have done their work. If they've done it well, then we'll have a good chance of success," Repsol spokesman Kristian Rix said by phone from Madrid. "It's been a long process, but now we're at the point where we discover where our geologists have got it right. It's a happy day."

Cuba's offshore oil dreams have stirred up controversy in the United States and become yet another cause for squabbling between officials in the United States and Cuba.

Their proximity has also prompted fears that a massive spill like the 2010 Macondo-Deepwater Horizon disaster could foul not just Cuba's reefs and gleaming, white-sand beaches, but also the coast of Florida and potentially the Atlantic Seaboard up to North Carolina.

Although U.S. inspectors gave the Scarabeo-9's safety systems a clean bill of health last week during an inspection in Trinidad, Cuba would be hard-pressed to respond to a major spill on its own, and getting help isn't as simple as making a phone call to Washington.

Under the U.S. embargo, any American companies, personnel and equipment contracting with Cuba on oil must get an exemption from the U.S. government. But so far, few of those licenses have been issued.

"Of all of the resources that were required to cap the well on Macondo ... less than 5 percent of those have been licensed by the U.S. government," said Lee Hunt, president of the International Association of Drilling Contractors.

Studies estimate that Cuba may have anywhere from 5 billion to 9 billion barrels of crude offshore, though the exact size of the reserves is still unquantified and production will take years to come online.