The continued detention of two Greek soldiers by Turkey is one of the key issues that Prime Minister Alexis Tsipras will be discussing with Greece’s allies at the NATO Summit in Brussels, government spokesman Dimitris Tzanakopoulos said on Tuesday.

“The issue will be raised by the prime minister in all of his addresses and meetings, so as to exert the maximum pressure for their release,” he said in reference to Lieutenant Angelos Mitretodis and Sergeant Dimitris Kouklatzis, who were arrested on March 1 after accidentally straying into Turkish territory while on border patrol in northeastern Greece in a storm.

In a related development, the European Commission’s high representative for foreign affairs, Federica Mogherini, is reported to have sent a letter to the chair of the European Parliament’s Foreign Affairs Committee, David McAllister, calling for continued solidarity with Greece over the issue of the soldiers’ detention.

NATO’s leaders are meeting in Brussels on Wednesday and Thursday where, among other topics, they will also discuss the Former Yugoslav Republic of Macedonia’s bid to join the alliance after coming an agreement with Greece last month with regards to its name and other disputes that have blocked its accession ambitions for more than two decades.