BRUSSELS: The EU warned Tuesday that all options were still on the table to defend its interests if Turkey does not engage "constructively" in attempts to ease a territorial dispute in the eastern Mediterranean.

Turkey, Greece and Cyprus have been locked in a row over energy resources and contested maritime borders in the region, with Ankara infuriating the EU countries by sending research ships with naval escorts to work in contested waters.

Athens and Ankara have said they are ready to talk to try to solve a crisis that will be discussed at an EU leaders' summit Thursday and Friday in Brussels.

In his invitation letter, the president of the European Council, Charles Michel, said that a dinner on Thursday evening would be devoted exclusively to the situation in the eastern Mediterranean and relations with Turkey.

"Our objective is to create a space for a constructive dialogue with Turkey to achieve stability and security in the whole region, and to ensure full respect for the sovereignty and sovereign rights of all EU member states," he wrote.

"This will only be possible if Turkey engages constructively. All options remain on the table to defend the legitimate interests of the EU and its member states."

The situation in Belarus, the alleged poisoning of Russian opposition leader Alexei Navalny and fighting in the breakaway region of Nagorny Karabakh are also on the programme of the European summit.