Manny Pacquiao weighed in one pound lighter than American Floyd Mayweather after the Filipino was welcomed by deafening cheers from his supporters on the eve of Saturday's hotly anticipated welterweight showdown in Las Vegas.

Pacquiao, 57-5-2 (38 knockouts), tipped the scales at 145 pounds in front of a massive crowd at the MGM Grand Garden Arena where fans purchased tickets to gain entry.

Undefeated Mayweather, 47-0 (26 KOs), a 2-1 favourite for what has been billed as the 'Fight of the Century', was weighed second, hitting the scales at 146 pounds for the scheduled 12-round megabout.

The showdown between the two best boxers of their generation has been more than five years in the making and is expected to be the biggest-grossing prize fight of all time.

What had been a subdued build-up to the most anticipated fight in decades exploded to life when Pacquiao and then Mayweather entered the arena to thumping hip hop music and deafening cheers from a seething crowd of 11,500, some of whom had waited three hours for a glimpse of the two boxers.

Their meeting is expected to be the biggest grossing prize fight of all-time.

"I have dedicated myself to the sport of boxing for the last 20 years and I am ready," declared Mayweather over a roar of boos and cheers.

Asked for a prediction about the fight, the 38-year-old American said, "I can't really say but I am ready to fight. It's an unbelievable turnout. I'm glad all the fans came out to here to support Manny and me."

Normally free and open to the public, the weigh-in broke from tradition, charging to watch Mayweather and Pacquiao step onto the scales in a move designed to maintain crowd control.

All money raised through ticket sales went to charity, but many of the tickets found their way onto the resale market.

A smiling Pacquiao, dressed in a bright red track suit, waved and raised his fists into the air as he slowly made his way to the stage, playfully interacting with the crowd.

In stark contrast, Mayweather was serious and focused, rarely looking up from under the brim of his 'Money Team' baseball cap to reveal a cheeky smirk.

Once the business of the official weigh-in was complete, the two welterweights moved to the front of the stage for the traditional stare down, the smaller Pacquiao looking up at Mayweather with a challenging smile while the stone-faced American stared straight-ahead unmoved.

"I have been fighting bigger guys like (Antonio) Margarito and (Oscar) De La Hoya," said the Filipino southpaw.

"It doesn't matter to me. I feel tomorrow that the Lord is always with me and gives me strength. "I know it's a great, great responsibility for me to give enjoyment to the fans. "Tomorrow the fans deserve to have a great fight."

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