Ukraine's foreign ministry criticised Croatian President Zoran Milanovic on Tuesday for saying Crimea would never return to Ukrainian control, describing his comment as 'unacceptable'.

In remarks on Monday detailing his objection to Zagreb providing military aid to Kyiv, Milanovic said it was 'clear that Crimea will never again be part of Ukraine'.

'We consider as unacceptable the statements of the president of Croatia, who effectively cast doubt on the territorial integrity of Ukraine,' Ukrainian foreign ministry spokesperson Oleg Nikolenko wrote on Facebook.

Milanovic on Monday declared it is 'mad' to think that Russia can be defeated in a conventional war and criticised western nations for supplying Ukraine with heavy tanks and other weapons.