MAYWEATHER TO RETIRE AFTER MCGREGOR FIGHT

Jeff Horn's hopes of facing Floyd Mayweather may be dashed after the American boxer announced his retirement

Jeff Horn's hopes of facing Floyd Mayweather appear to be dashed after the American boxing great announced next month's fight with UFC lightweight champion Conor McGregor will be his last.

Horn, who this month beat Manny Pacquaio to win the WBO welterweight title in Brisbane, has called out the 40-year-old five-division world champion.

But Mayweather ruled out any prospect of a fight with the former Queensland schoolteacher.

At a packed press conference in London on Friday, Mayweather said he'll hang up his gloves for good after facing McGregor on August 26 in Las Vegas.

'This is my last fight,' Mayweather said.

'I've just done years and years and years of just fighting and travelling.

'I gave my word it is going to be my last fight, I promised this will be my last fight.'

'I thought the Pacquiao fight would be my last fight but I am still in business and this fight is good business.'

Horn called for Mayweather, who is unbeaten in his 49 professional bouts, immediately after beating Pacquiao and has been campaigning for the fight ever since his stunning victory over the Filipino.

The Australian spent much of this week in America predicting a Mayweather victory next month and again declared he'd love a crack at the biggest box office draw in the fight game.

'To get a fight with Mayweather would be massive,' Horn told News Corp Australia earlier in the week.

'My trainer Glenn Rushton is already working on a plan to beat him.

'And why not? I just beat Manny Pacquiao.'

While Horn won't get the fight he so craves with Mayweather, the American did have praise for the way he saw off his one-time great rival, who he outpointed in May 2015.

Mayweather is an overwhelming favourite to beat McGregor, who has never boxed as a professional, but admitted to concerns of an upset similar to the one Horn delivered on Pacquiao.

'It's just like the Pacquiao situation,' Mayweather said.

'I think Pacquiao was focused on fighting (me) again. No one gave Jeff Horn a chance -- he's a schoolteacher who was bullied -- now he's world champion.

'So anything can happen in boxing.'