Spanish oil major Repsol-YPF said Thursday its plans to explore for oil in Cuban waters strictly comply with U.S. law governing a decades-old trade embargo on the communist-ruled island.

A group of 34 Democratic and Republican lawmakers in the U.S. House of Representatives sent a letter to Repsol Chairman Antonio Brufau warning that the company could face legal action in the United States if it does not abandon its offshore drilling plans.

"Any drilling operations that Repsol conducts in Cuban waters will provide direct financial benefit to the Castro dictatorship," the lawmakers said.

They also suggested that "Repsol may be in jeopardy of subjecting itself and its affiliates to criminal and civil liability in U.S. courts."

Repsol spokespersons told Efe they also are complying Cuba law governing their activities and that all of Repsol's operations in Cuban waters are being conducted under the highest quality and safety standards.

Repsol is one of several foreign oil companies, including Venezuelan state-owned giant PDVSA and PetroVietnam, with offshore drilling plans in Cuba's Exclusive Economic Zone of the southeastern Gulf of Mexico.

The zone, which is estimated to hold up to 9 billion barrels of petroleum, covers some 112,000 sq. kilometers (43,240 sq. miles) and is divided into 59 blocks of 2,000 sq. kilometers (772 sq. miles) each.