St-Pierre is the current welterweight champion, cutting down to make the 170-pound weight limit the day before he fights. Silva, the middleweight title-holder, has to make 185 although he has also fought as a light-heavyweight (205 pounds).
Considering Silva is the bigger man, the GSP camp has suggested he come down in weight to meet them. UFC president Dana White has suggested the fight be contested at 177 or 178 pounds, between their two weight classes.
Penn, a former lightweight (155) and welterweight champion who has competed in a variety of weight classes, suggested Tuesday says he would fight rather than dicker over weight.
"That fight, that's on Georges himself," Penn told a media conference call. "But everybody on this phone call knows what B.J. Penn would do.
"You know what I would do if Dana called me to fight the champion (in the weight class) above."
Earlier in the call, White said he had nothing to report on a possible GSP-Silva fight, saying St-Pierre has been on holiday since defeating Carlos Condit at UFC 154.
Penn, who has lost twice to St-Pierre, fights Canadian welterweight Rory (Ares) MacDonald on Dec. 8 on a televised card in Seattle.