LAS VEGAS - Unbeaten US star Floyd Mayweather threw down another provocative gauntlet to boxing rival Manny Pacquiao on Tuesday, daring the Filipino icon to "Step up Punk" in a posting on his Twitter web page.

LAS VEGAS - Unbeaten US star Floyd Mayweather threw down another provocative gauntlet to boxing rival Manny Pacquiao on Tuesday, daring the Filipino icon to "Step up Punk" in a posting on his Twitter web page.

Mayweather hopes to entice Pacquiao into accepting his challenge to meet on May 5 in Las Vegas in a mega-fight between the world's top pound-for-pound fighters, one that boxing fans have wanted to see for years.

"Manny Pacquiao I'm calling you out let's fight May 5th and give the world what they want to see," Mayweather posted on Twitter.

The move comes as Pacquiao's promoter Bob Arum is visiting him in the Philippines to discuss who the Asian superstar should fight next and Mayweather awaits the June 1 start of a 90-day jail sentence on domestic violence charges.

Arum originally said that Mayweather was not among possible next foes for "Pacman", listing Mexico's Juan Manuel Marquez and Americans Tim Bradley and Lamont Peterson as candidates. But that was assuming Mayweather was going to start serving his sentence last week. Instead, a judge postponed Mayweather's trip behind bars until after his May 5 fight that has already been booked.

"My jail sentence was pushed back because the date was locked in. Step up punk," Mayweather also tweeted on Tuesday.

Pacquiao, who has won 15 fights in a row over the past seven years, has told Filipino media that he wants the opportunity to fight Mayweather to be a top priority. Mayweather, who squandered a chance to seal a fight with Pacquiao earlier by seeking extraordinary blood testing measures, hopes to pile the pressure on Arum and Pacquiao with his Twitter challenge.

But Arum has laughed off Mayweather's May 5 plan, saying he could secure $20million (R162million) more with the construction of a temporary venue in Las Vegas to stage such a long-awaited fight before more than twice as many spectators.

Critics see that and other moves as Arum wanting to avoid pitching Pacquiao, 54-3 with two draws and 38 knockouts, against Mayweather, 42-0 with 26 knockouts.

Both fighters are coming off controversial victories. Pacquiao, a 33-year-old southpaw, won a majority decision over Marquez in November last year, giving him two wins and a draw over the Mexican but none of them by such a margin that Marquez's claims he was wronged could be dismissed.

Mayweather, who turns 35 next month, won the World Boxing Council welterweight title with a fourth-round knockout of compatriot Victor Ortiz, but he landed the decisive blow while Ortiz was distracted after the referee had separated the fighters.