Jean Pascal, left, and Bernard Hopkins, shown here at the weigh-in prior to their December draw, will fight again on May 21 in Montreal. ((Jacques Boissinot/Canadian Press))

A news conference in Montreal to promote a WBC light-heavyweight title fight turned into a shoving match Monday when champion Jean Pascal suggested that he and veteran Bernard Hopkins submit to blood tests before and after the bout.

Security guards moved in to separate the fighters when Hopkins gave Pascal a shove and the Montreal boxer pushed back.

Pascal said he believes Hopkins is clean but that some fans suspect he may he using performance-enhancing drugs. The 46-year-old Hopkins is hoping to become the oldest fighter to win a major world title.

He says "it's to show the fans that we are clean fighters and that boxing is a clean sport."

Hopkins called Pascal a "scared punk" who was preparing excuses in advance in case he loses the May 21 bout at the Bell Centre.

The bout will be a rematch of their meeting Dec. 19 in Quebec City that ended in a majority draw.