France's presidential election finalists are to debate Wednesday, in a two-hour, televised event ahead of this Sunday's vote.

The debate between conservative frontrunner Nicholas Sarkozy and Socialist Segolene Royal begins at 9:00 p.m. local time (1900 UTC) and is expected to draw more than 20 million French viewers - an audience size usually reserved for World Cup soccer finals.

The latest opinion poll shows Sarkozy maintaining at least a four percentage point lead over Royal.

On Tuesday, the fourth-place finisher in the April 22 first-round vote, ultra-conservative Jean-Marie Le Pen, urged his supporters to boycott the run-off election. The third-place finisher, centrist Francois Bayrou, has not formally backed either candidate.

Some information for this report was provided by AFP, AP and Reuters.