The plots are located in four large areas that seismic studies indicate may have significant hydrocarbon reserves.

One stretches from the north of Corfu close to the Albanian border down to the islands of Paxos and Antipaxos, a second is of the coast of Kefalonia, another off the coast of Katakolos were rights have already been granted for exploration, while the fourth is located south of Crete reaching the border with Libya.

The blocks cover a combined area of more than 200,000 square kilometers.

At the event Mr Maniatis will present the findings of Petroleum Geo-Services, which has been conducting seismic tests in Greek waters. In attendance will be 150-200 representatives of most major oil companies including ExxonMobil, Chevron, Shell, Norway's Statoil, the Italian Eni and Edison and the German E.ON among others.

According to Reuters while the ministry has described PGS's findings as 'encouraging, “Energean Oil & Gas, Greece's only domestic oil producer, doubts that large deposits will be found.”

But in a recent interview with Kathimerini, Mr Maniatis was more optimistic saying, “We now know for sure that there are hydrocarbons in Greece and that exploring for them makes economic sense.”

The Greek government has already granted the exploration rights to three blocks both on land and offshore.

The official announcement of the tender is expected to be published in the European Gazette immediately following the event with oil companies given at least 90 days to prepare their bids, meaning that the process is expected to be completed towards the end of the year.