A bloodied Tim Tszyu has been cruelly denied in his quest to emulate his legendary father Kostya and become a unified world boxing champion after a sapping loss to towering American Sebastian Fundora.

Suffering his first defeat in 25 fights, Tszyu surrendered his WBO super welterweight belt and the vacant WBC strap in Las Vegas, missing his chance to take his place among the sport's elite.

Tszyu lost the fight in a split decision, with the judges scoring the fight 116 -112, 115-113, 112-116 in favour to Fundora.

"Look, I told you, I'm an old throwback fighter whatever circumstances. I couldn't see but all credit belongs to the man who won tonight," Tszyu said.

"These things happen. The momentum was rolling. I was swinging hard in the first rounds and then 'boom', you're blinded completely.

"But, look, this is boxing. This is part of the sport and it happens.

"Congratulations to Fundora  he's the new king at 154 (pounds)."

The unlucky Australian's fight derailed at the end of the second round when he walked into the elbow of 197cm Fundora, opening up a huge gash on his head.

The world champion had dominated the opening exchanges, putting his tall-timber opponent on the back foot with some heavy right-hand blows.

Despite blood pouring down his face, Tszyu was cleared to continue by the fight doctor but Fundora took advantage of the Australian's lack of vision to level the score.

With both fighters covered in blood, with Fundora's nose also gushing, the Australian continued to search for a way to bring the battle to an early end.

Fundora played it smart by trying to attack Tszyu's head while the Sydney warrior, using his gloves to wipe the blood from his eyes, was unable to connect in his usual fashion.

With Fundora edging ahead, the doctor again checked the cut at the start of the seventh round but gave the green light for it to go on.

Like a gladiator, Tszyu battled on as he hunted a knockout blow but hindered by the blood flow he was unable to stop the Californian.