The Luxembourg Presidency is not intending to change the agenda, which has already been sent to member-states, the source said.
However, an informal discussion on Croatia as an item in the other business discussion is not ruled out. In any case the summit of EU heads of state or government will not consider a change to the decision on the postponement of the negotiations, which was made by the EU foreign ministers on 16 March, the source added.
Last Wednesday, the EU foreign ministers decided to postpone the opening of Croatia's membership talks, previously set for 17 March, until the Union reaches consensus on whether Croatia is fully cooperating with the Hague-based UN war crimes tribunal.
The same source said today that it was reported by mistake that five EU members had asked for next week's discussion on Croatia, as one request was counted as two requests since it was sent both by e-mail and as a letter.
It was not officially confirmed which four countries were for the discussion. Some diplomatic sources said that Slovenia and Austria moved the item while Hungary and Slovakia are believed to be the other two.
Prime Minister of Luxembourg, Jean-Claude Juncker, who is the chairman of the European Council, already sent official invitations to EU member-countries' heads of state or government to attend Tuesday-Wednesday summit in Brussels.
On Tuesday, they are expected to discuss a reform of the pact on stability and growth, and on Wednesday they are to consider a reform of the Lisbon strategy.
Foreign and finance minister will hold separate sessions in Brussels in the same period.
At the end of the summit, the Luxembourg Presidency will inform leaders of countries-candidates, including Croatia's Prime Minister Ivo Sanader, of the results of the two-day meeting.
On Tuesday, Sanader will attend a meeting of the European People's Party (EPP) leaders. The EPP traditionally convenes on the eve of the every EU summit.