The French president has decided to leave an EU summit just before a meeting with interim Iraqi Prime Minister Iyad Allawi.
Mr Chirac says he is busy and will not attend the meeting
Mr Allawi is due to join EU leaders as guest of honour at the summit lunch in the Belgian capital.
But Jacques Chirac, an outspoken critic of the war in Iraq, says he has prior engagements and will not attend.
Meanwhile, UK leader Tony Blair has said some EU leaders are in a "state of denial" over President Bush's poll win.
Mr Blair has urged European leaders to accept President Bush's re-election in an interview with London's Times newspaper.
Correspondents say Mr Chirac's move is seen as a clear snub to Mr Allawi who has called for broader involvement in Iraq.
Mr Allawi has implored so-called "spectator countries" to become actively involved in the reconstruction of Iraq.
The EU leaders are expected to present a multi-million dollar aid package to Mr Allawi at the meeting.
The money will be used to provide technical advice and support for the Iraqi elections, planned for January.
Mr Allawi, on a European tour, made his plea for wider participation in his country after a meeting with Italian Prime Minister Silvio Berlusconi in Rome on Thursday.
The BBC's Tim Franks, in Brussels, says one EU foreign minister said his comments were pointed rather than helpful.