Curtis Jackson, the rap music star better known as 50 Cent, says he will bet $US1.6 million ($A2.06 million) on pal Floyd Mayweather to beat Manny Pacquiao in their May boxing showdown.

The much-anticipated bout will be staged May 2 in Las Vegas and could be the richest payday in boxing history for undefeated Mayweather.

“Champ is going to do it. He’s going to smoke him,” Jackson told radio station Power 105.1. “It’s going to look like he pumped up for no reason.”

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Asked if he would back up his confidence with a bet, Jackson replied, “Probably like 1.6 (million). I’ve been thinking this out. I’m going to make a real bet. He’s focused right now.”

Jackson last year taunted Mayweather’s reading ability after a radio station aired audio of the fighter struggling to read a promotion transcript. He challenged the US fighter to read a page from a Harry Potter book in exchange for a $US750,000 ($A965,000) donation by Jackson to charity.

Mayweather responded with a Twitter posting featuring a photo of two massive cheques saying, “Read this $72,276,000.00 God bless.”

Jackson compared his spats with Mayweather to a married couple taking out frustrations over other things on each other.

“We can both get madder when we’re not speaking to each other,” he said.

Filipino southpaw Pacquiao is 57-5 with two drawn and 38 knockouts while Mayweather is 47-0 with 26 knockouts.

On Australian betting agency Sportsbet, Mayweather is a $1.40 favourite, with Pacquiao at $2.90.