His strong criticism comes after Mr Kostunica said that a regular government meeting scheduled for Thursday (7 February), which was to give the green light to deputy prime minister Bozidar Djelic to travel to Brussels and sign the EU deal, will not be held.
The prime minister requested an urgent session of the Serbian parliament instead, in order "to confirm the national unity in the defence of Kosovo-Metohija" and to avoid political destabilisation, according to the website of the Serbian government.
Meanwhile, sixteen ministers as well as Serbian deputy premier Bozidar Djelic have sent Mr Kostunica a letter asking him not to block Thursday's cabinet meeting.
"We hereby ask you to schedule a regular government session for Thursday, February 7, 2008, at which, among other things, the government will decide on its stance towards the political agreement on cooperation between the EU and its member countries on the one side, and Serbia on the other", the letter reads.