Tim Tszyu fires back at Jermell Charlo after the undisputed super welter champ mocked his last name

Tim Tszyu has fired back at Jermell Charlo as the verbal diatribe between the two boxers went up a notch.

The American became the undisputed super welterweight world champion on Saturday night, defeating Brian Castano to add the latter’s WBO belt to his own IBF, WBC and WBA titles.

Tszyu is the mandatory challenger for Charlo’s newly-acquired WBO title, but the undisputed champ bristled at questions over a potential bout with the Australian in the future.

‘F**k you and Tim Kazoo! Change the mic,’ was Charlo’s response after being asked whether he planned to fight the Sydney boxer.

Tszyu, who was among the ringside spectators as Charlo stopped Castano in the 10th round in Los Angeles, poured more petrol on the fire.

‘He’s a very disrespectful man, so stuff him. I don’t like him anyway,’ he told Fox Sports.

‘I think me and him will sell because there’s no love between us two – it’s all hate.’

Charlo (right) delivered a masterclass as he beat Argentina’s Brian Castano 

The American stopped his rival with a brutal hit in the 10th round, his 19 KO win in 35 bouts

By claiming the WBO belt Charlo (right) has unified the super welterweight division 

The 27-year-old, who is still undefeated 21 fights into his professional career, then called out his rival warning him he would have to vacate the title if he refused to get in the ring.

‘If you want a dance partner, I’m here. I’m here to try to take you out. If you want to punch on I’m always keen,’ the Australian added.

‘I’m the mandatory challenger. He has a few months to make a decision or he vacates the belt. Fight me or vacate – that’s all there is.’

George Rose, the chief executive of No Limit, which promotes Tszyu, said negotiations were already underway in LA for WBO showdown.

With Tszyu (left) now his mandatory challenge for the WBO belt Charlo just claimed 

It’s now time for politics and negotiating. Tim’s done the hard work getting to this position, now we have to convince Charlo to take this fight or he has to vacate.

‘I love that they [Charlo’s camp] pretend they don’t know Tim but when he [Charlo] says that Tim doesn’t deserve to fight him he’s saying that because he doesn’t want to fight him – Tim is the most dangerous guy in the super welterweight division.’

Tszyu is also the second and third in line for Charlo’s WBC and IBF belts respectively, with the American facing mandatory title defences against Sebastian Fundora for the former and Bakhram Murtazaliev for the latter.

Meanwhile, the WBA has ordered a rematch between Israil Madrimov and Michel Soro to determine who should be its mandatory challenger.