Libya’s eastern-based parliament has backed a 2019 maritime deal with Turkiye already signed by the North African nation’s internationally recognised government based in Tripoli to delimit maritime boundaries in the Mediterranean Sea.

The vote on Tuesday came as Turkiye has been cultivating close ties in recent years with the eastern parliament, backed by renegade military commander Khalifa Haftar. Ankara had helped the Tripoli government, known as the Government of National Accord (GNA), push back an offensive in 2020 by Haftar’s self-styled Libyan National Army (LNA) that aimed to capture Tripoli. Egypt and the European Union have rejected the ratification of the maritime borders agreement, calling the deal “null and void”.

On Tuesday, the Tobruk-based House of Representatives voted unanimously to approve the agreement, reversing its 2020 rejection.

Israel also condemned the move while Greece, which said the agreement violates international law, briefed the United Nations Security Council. Turkish Foreign Minister Hakan Fidan dismissed the criticism, calling the deal “entirely legitimate”.

So what is the deal, and why has it drawn such a backlash? Here’s what you need to know:

What is the deal? It is a memorandum of understanding that draws a sea border between Turkiye and Libya across the eastern Mediterranean.

It was signed in Istanbul on November 27, 2019, by Turkish President Recep Tayyip Erdogan and Fayez al-Sarraj, then-prime minister of the UN-recognised government in Tripoli.

Within weeks, Turkiye sent drones and military advisers to help repel Haftar’s assault on Tripoli. The deal allowed Ankara to claim large and potentially gas-rich areas of the eastern Mediterranean.

Turkish Foreign Minister Hakan Fidan, right, meets with General Saddam Haftar, deputy commander of the self-styled Libyan National Army, in Ankara, Turkiye [File: Handout/Turkish Ministry of Foreign Affairs] Why does Egypt oppose it? Because Cairo says it cuts into Egyptian waters.

Egypt’s Ministry of Foreign Affairs said the agreement “constitutes a clear infringement upon Egypt’s sovereign rights within its exclusive economic zone and continental shelf”. It said the ratification “carries no legal consequences for Egypt”.

President Abdel Fattah el-Sisi has historically been one of Haftar’s strongest backers, but experts said their relations have cooled because Haftar allowed his territory to be used to funnel support to the Rapid Support Forces (RSF) paramilitary group, which is fighting Sudan’s military, the AFP news agency reported.

Cairo is also now a close security ally of Ankara, and in July, Egypt refrained from objecting to a maritime line drawn between Benghazi and Turkiye.

According to exclusive information Al Jazeera received in July, the rapprochement between Ankara and Haftar’s general command included agreements on developing military facilities and advanced surveillance systems.

The agreements also included training programmes in Turkiye for eastern Libyan officers with specialised Turkish defence companies participating in the projects.

Wolfgang Pusztai, a security policy analyst and former Austrian defence attache in Greece, told Al Jazeera that a possible Turkish military presence in eastern Libya was “probably more of a concern for Egypt”.

“This is not so much an issue for Greece, which has a Turkish military presence next door anyway,” he said, adding, “I doubt Cairo would accept this.”Security forces stand guard outside the parliament building in Tobruk, Libya [File: Esam Omran Al-Fetori/AP Photo] Why does the EU oppose it? Because two of its member states said it seeks to take their waters.

In a joint statement on Tuesday, European Council President Antonio Costa and European Commission President Ursula von der Leyen said the memorandum infringes on the sovereign rights of third states and does not comply with the UN Convention on the Law of the Sea (UNCLOS). They reaffirmed the bloc’s solidarity with Greece and Cyprus.

Athens said the deal ignores Greek islands, including Crete, Rhodes and Karpathos, and therefore infringes on its maritime territory, according to a briefing document from the Greek Ministry of Foreign Affairs.

Sotirios Zartaloudis, an associate professor in comparative European politics at the University of Birmingham, told Al Jazeera that Athens and Nicosia see the deal as a Turkish attempt to block the “crucial Great Sea Interconnector”.

The planned subsea power cable, which would link Greece’s grid to Cyprus and later Israel, has been delayed by a dispute between Athens and Ankara over waters off the Greek island of Crete, the Reuters news agency reported last year. The project is estimated to cost about $2.1bn.

Turkiye has not signed UNCLOS, which means Ankara is not bound by the treaty’s rules governing maritime boundaries.

On Wednesday, EU foreign policy chief Kaja Kallas urged all countries to respect member states’ sovereign rights under EU and international law, including UNCLOS.

Zartaloudis said both countries had pushed for the EU to condemn the deal, but “so far expectations were not met”, and that “they will try to gain further support against the deal”.

He added that “the main actor in the region is the US”, which he said had not repudiated the agreement. What does Turkiye say? Ankara said the deal is lawful and already in force.

Turkiye’s Ministry of Foreign Affairs said the memorandum safeguards both countries’ rights on the basis of international law and “the principle of equity”.

“There are countries reacting to this. We know why they are reacting,” Fidan told state media.

“However, this is an entirely legitimate deal, both from a legal and a statutory perspective,” he said. Why did eastern Libya change its mind? Because Ankara has spent years courting it and its parliament has new leadership.

After Ankara struck a deal with Haftar’s LNA in July, the eastern parliament on October 6 elected Al-Salhin Abdelnabi al-Obeidi as speaker, replacing Aguila Saleh after more than 12 years. Al-Obeidi previously chaired the Libyan-Turkish parliamentary friendship committee.

Anas El Gomati, director of the Sadeq Institute, a Libyan think tank, told Al Jazeera that the turnaround in eastern Libya was about the route to the presidency under a US mediation plan for Saddam Haftar, Khalifa Haftar’s son and deputy commander.

“Turkiye is now the most consequential outside power in Libya with leverage over Tripoli and a military presence in the west, and he needs it to get there and to stay there,” El Gomati said.

“But a ratified treaty is hard to reverse, so Ankara gets something that looks permanent in return for support that, depending on how the Haftars use it, may not be,” El Gomati said. Does the vote unite Libya’s rivals? Not on the issues that divide them most.

Tripoli’s GNU welcomed Tuesday’s vote, meaning both of Libya’s rival centres of power now back the deal. But El Gomati said the “unification was never about the sea”.

“It’s about who controls the budget, the army and the electoral commission, and this vote touches none of them,” he said. What happens next? Athens said it would take all appropriate measures to safeguard its sovereign rights.

El Gomati said implementation now depended on institutions such as Libya’s National Oil Corporation and he expected pressure “to be diplomatic and slow”.

Pusztai said the risk of naval incidents if Turkiye or Libya act on the deal at sea was “very high”.

He said it might also lead to the involvement of the EU naval mission enforcing the UN arms embargo on Libya since 2020.

In August 2020, months after the deal was signed with the GNU, Ankara sent the survey vessel Oruc Reis to explore for oil and gas in waters Greece claims, bringing the two NATO allies to the verge of military confrontation.