Great Sea Interconnector explained: the Greece–Cyprus cable and the law of the sea

The Great Sea Interconnector (GSI) is a planned undersea electricity link that would connect Crete, Cyprus and Israel and end Cyprus’s status as the last EU member state without an electricity interconnection. It is in the news this week because the cable ship Abeille Marengo has resumed seabed surveys south of Kasos, and Ankara has declared the Greek and Cypriot navigational warnings for that work “cancelled”.

Key points

• The project is on the EU’s list of Projects of Common Interest, and the Connecting Europe Facility has granted €657 million for the Greece–Cyprus interconnection.
• The Greece–Cyprus section is about 900 km of subsea route with an initial capacity of 1,000 MW, according to the project’s own website.
• Under the UN Convention on the Law of the Sea (UNCLOS), all states may lay submarine cables on the continental shelf, and a coastal state “may not impede” the laying.
• Turkey, which is not a party to UNCLOS, says the surveys need its consent in an area it claims as its own shelf. Greece has licensed the work as the coastal state.

What is the Great Sea Interconnector?

The GSI is a high-voltage direct-current (HVDC) cable system. Greece’s transmission operator IPTO (ADMIE) describes the company behind it, Great Sea Interconnector S.A., as a special purpose vehicle of IPTO set up in January 2024, and presents the project as a Crete–Cyprus link with Israel as the next phase (IPTO project page). The aim, in IPTO’s words, is to connect Cyprus, “the last non-interconnected EU Member State”, to the European transmission system.

The project website lists a long pedigree: the EuroAsia Interconnector initiative began in 2012, the scheme entered the EU’s first Projects of Common Interest list in 2013, Greece, Cyprus and Israel signed a memorandum of understanding in 2021, and in 2022 the EU secured €657 million in Connecting Europe Facility financing for the Greece–Cyprus interconnection. In August 2026 Meridiam and IPTO signed an agreement making Meridiam the majority shareholder of the GSI company (Great Sea Interconnector).

Key figures

Why does Cyprus need it?

Cyprus is an electricity island: it sits at the edge of the EU grid with no cable to any neighbour. IPTO says the Cyprus–Israel leg would also improve Israel’s security of supply and let it expand renewable energy faster. In August 2026 IPTO filed an investment request with the regulators of Cyprus and Israel under the EU’s TEN-E framework, saying the cost-benefit studies “confirm the economic viability of the project in all analyzed scenarios”. The regulators must now agree on cost allocation, after which a final investment decision would open the project financing (IPTO announcement). Those are IPTO’s own findings and have not been tested by the regulators yet.

What does the law of the sea say about laying a cable?

The text of UNCLOS is unambiguous on the principle. Article 79(1) says: “All States are entitled to lay submarine cables and pipelines on the continental shelf.” Article 79(2) adds that the coastal state, subject to reasonable measures for exploring and exploiting the shelf and controlling pollution from pipelines, “may not impede the laying or maintenance of such cables”. Article 58(1) gives all states the same freedom in the exclusive economic zone (UNCLOS, full text).

Consent comes in at one narrow point: Article 79(3) makes the delineation of the course for laying pipelines on the continental shelf subject to the consent of the coastal state. The article speaks of pipelines, not cables, and the coastal state’s role over cables is limited to measures such as those in paragraph 2.

Greece’s case rests on Article 121(2): the territorial sea, the exclusive economic zone and the continental shelf of an island “are determined in accordance with the provisions of this Convention applicable to other land territory”. Crete, Kasos and Karpathos are inhabited Greek islands. On that reasoning, the seabed south of Kasos lies on the continental shelf of Greece and, further east, of Cyprus, two coastal states that are both parties to UNCLOS and members of the EU. For the wider legal framework, see our earlier explainer, UNCLOS explained: sea zones, islands and the Aegean dispute.

Ankara’s case

Turkey does not accept that reading. In Statement No. 214 of 6 November 2026 its foreign ministry says that a French-flagged vessel intends to carry out marine scientific research without authorisation on what Ankara calls its continental shelf, that it has cancelled the navigational warnings issued by Greece and the Cypriot authorities, and that the consent procedure for the part of the work inside its claimed shelf has not been completed. It points to the outer limits it notified to the United Nations on 18 March 2020 (Turkish Ministry of Foreign Affairs, Statement No. 214).

These are Ankara’s claims, and they rest on a convention Turkey has not joined, while Greece, Cyprus and the EU are parties. Turkey’s claimed limits depend on the Turkey–Libya memorandum and disregard the shelf of islands such as Kasos, Karpathos and Crete, which Article 121(2) says is determined like that of any other land territory.

What has happened at sea?

The surveys are not new. As we reported at the time, the Abeille Marengo stopped work south of Kasos in 2024 after Turkish warships moved close to a survey vessel in the area in July 2024. This month Greek and Cypriot NAVTEX warnings reopened the work: the Greek Navy’s Hydrographic Service issued NAVTEX 1411/26 for surveys from 6 November 2026 to 6 March 2027, starting where the earlier work was halted, after Foreign Minister George Gerapetritis signed the licence following a positive opinion from an interministerial committee. Ankara answered with counter-NAVTEX 1105/26 and the statement above. See our reports on the NAVTEX for the Abeille Marengo, the Turkish statement that cancels the NAVTEX and the earlier Abeille Marengo departure for Heraklion.

Why Cyprus is part of the picture

The cable is meant to end the isolation of a state whose northern part has been under Turkish occupation since the 1974 invasion, a situation the UN peacekeeping force UNFICYP has patrolled since 1964 (see UNFICYP explained: the UN force in Cyprus since 1964). Turkish naval pressure on survey ships working for an EU-backed project in Greek and Cypriot waters is an obstruction of lawful activity under the convention quoted above, and it comes from the same state that continues to occupy part of an EU member.

What remains open

Three things decide whether the cable is built: the Cyprus–Israel regulatory approvals and final investment decision described by IPTO, the completion of seabed surveys that were halted in 2024, and the response at sea to the work now under way. None of these can be predicted from the documents above, and the article does not attempt to.

Sources

IPTO (ADMIE): Great Sea Interconnector; IPTO: Cyprus–Israel investment request, 13 August 2026; Great Sea Interconnector project website; United Nations Convention on the Law of the Sea, text; Turkish Ministry of Foreign Affairs, Statement No. 214.