* Cuba says expropriation of Repsol shares a sovereign right
* Repsol a key Cuban partner in offshore oil exploration
HAVANA, April 19 (Reuters) - Communist Cuba on Thursday declared its support for Argentina's decision to expropriate a 51 percent controlling stake in the South American country's largest oil company, YPF, from Spanish owned Repsol.
"Cuba reiterates its solidarity with the Republic of Argentina and that this nation has a permanent sovereign right over all its natural resources," said a government statement, read on state-run television.
President Cristina Fernandez unveiled plans on Monday to seize Repsol's share of YPF, sparking a chorus of condemnation from Madrid to Washington and support from Venezuela and some other leftist governments in Latin America.
The brief Cuban statement accused Repsol of purchasing its controlling interest in YPF for less than its value.
The Spanish company is a key partner of Cuba's in its efforts to explore for oil off its northern coast in the Gulf of Mexico.
The company is currently drilling some 18 miles offshore in what has been billed as the start of exploration in a vast area thought to harbor billions of barrels of oil. (Reporting by Marc Frank; Editing by Todd Eastham)