LAS VEGAS (AFP) - Manny Pacquiao and Floyd Mayweather ramped up the anticipation for their blockbuster bout, feting fans on Tuesday before they get down to the final preparations for Saturday's welterweight showdown.

Tensions between the camps were evident as Filipino icon Pacquiao and his unbeaten American rival made public bows at separate venues.

"So many different sponsors and networks came together to make this big event happen - I think we both should have been here," Mayweather said after Pacquiao opted out of the "grand arrival" at the MGM Grand Garden Arena.

Pacquiao instead greeted fans down the street at Mandalay Bay.

The several hundred who attended his rally were far outnumbered by the thousands who turned out for Mayweather at the venue that will host the fight.

Most bookmakers have made 38-year-old Mayweather the favourite.

But 36-year-old Pacquiao told reporters he is revelling in his underdog status.

"I have something to prove. I like being the underdog because my killer instinct and my focus is there," he said.

Mayweather is confident he will get the job done.

"I truly believe I'm the smarter fighter," he said.

"I think everybody's game plan is to come forward and throw a lot of punches.

"It hasn't worked for 19 years - 47 fights, it hasn't worked," he noted of his track record.