Noble Company announced the discovery earlier this year in block 12, about 180 km off the coast, and the government of Cyprus decided to continue drilling despite strong objections from Turkey.
President Demetris Christofias, who face strong pressure to resign last summer in the blast munitions that destroy vital power plant nearby, made the announcement live on television on Wednesday.
Preliminary data emerging from the exploration and evaluation drilling, indicating the presence of natural gas reserves of 140 billion cubic meters to 224 billion cubic meters.
AFP news agency reported, although the amount was less than previous government estimates, around 283 billion cubic meters, more recent estimates that, if true, could meet the gas needs of the island country for decades.
President Christofias said that "the utilization of natural gas could be a solution for problems faced by Cyprus, which could end the illegal occupation, unite the country ... and restoring human rights and freedom of the people of Cyprus, including citizens of Greek descent and Turkish Cyprus.
Cyprus has been divided since 1974, when Turkish troops invaded and controlled the north of the island following a coup designed to unite Greece and Greek Cyprus.
In contrast to the whole international community, Turkey does not recognize the Cyprus government.
Noble Company won a tender exploration of oil mining in Cyprus in 2008.Since then Turkey has strongly protested the search for oil and natural gas offshore activities and called it "illegitimate"
Earlier, President Christofias said the discovery of gas would be a tool that will reconcile the region.