Balkan and eastern European leaders pose for a family photo at Maximos Mansion in Athens, Greece, Monday, Aug. 21, 2023. AP
Signed in the presence of Ukrainian President Volodymyr Zelensky, they expressed their "unwavering support for Ukraine's independence, sovereignty and territorial integrity within its internationally recognised borders" in the face of Russia's aggression.
Apart from Ukraine, the document was signed by the leaders of Serbia, Moldova, Montenegro, Romania, Kosovo, Bosnia and Herzegovina, North Macedonia, Bulgaria and Croatia, as well as Greece which was hosting the event.
European Council President Charles Michel and European Commission President Ursula von der Leyen also attended the summit.
The leaders also expressed their "support and appreciation for the earnest efforts by Ukraine's President Volodymyr Zelensky in setting out the principles for peace in line with the UN Charter."
Greek Prime Minister Kyriakos Mitsotakis's office said the gathering marked the twentieth anniversary of the 2003 Thessaloniki summit confirming the European perspective of Western Balkan states.
Zelensky visited Athens to attend the informal meeting, concluding a European tour with previous stops in Sweden, the Netherlands and Denmark.
Greece has said it will help train Ukrainian F-16 warplane pilots and assist the reconstruction of Odesa.
Kyiv on Friday welcomed a US decision to let Denmark and the Netherlands hand F-16 fighter jets over to Ukraine once its pilots are trained to use them.