Amir Khan keeps dancing, keeps moving and keeps out of range. 

Canelo keeps looking for the big punch that might end the contest and Khan keeps countering with sweet combinations.

A sweet right hand catches Canelo pretty flush in Khan's best moment so far.

It is eye-catching stuff. How much is it hurting Canelo though?

Khan was expected to shine in the first few rounds. Can he keep that up? 

Four-nil up and a third of the way there.

Paulie Malignaggi
Former welterweight world champion, speaking on BBC Radio 5 live

Image source, AP

"Canelo got a little closer that round but, for me, he still didn’t win it. Amir’s jab is putting him off and Canelo is losing his defensive position."

Canelo lands a clouting left early in the round. But Khan's chin passes that test.

And Khan replies with his own trademark strength, lightning hand speed pings Canelo. The Mexican looks a little startled by that flurry.

Khan is using every square inch of the ring to stay out of range before launching smash-and-grab raids.

Another little combination at the end of the round swings it Khan's way.

The Mexican fans are a lot quieter than at the start of the fight.

Paulie Malignaggi
Former welterweight world champion, speaking on BBC Radio 5 live

Image source, AP

"Another round for Amir Khan, for me. Amir has to be careful not to throw too many flurries though as that means Canelo is in his distance. 

"Amir moved out of his range in the last minute of that round and it is better for him to keep it boring.”

Canelo goes hunting, upping the speed of his own footwork to try and get Khan cornered.

Khan is nimble though and gets away from his pursuer again.

He is presenting a problem to Canelo - tying up the Mexican successfully when he gets too close in for comfort.

Plenty of street smarts from Khan so far. Canelo is struggling to get close enough in to his man and already has some swelling around his eyes.

I make that Khan's round again.

But all it takes is one moment from Canelo and this could be all over. This is a high-wire act for Khan.

Jordan Winter: Nice first round from @amirkingkhan, external he's moving well and just staying out of Canelo's range  

Paulie Malignaggi
Former welterweight world champion, speaking on BBC Radio 5 live

"I could not have thought of a better opening round for Amir. 

"He used his jab well and he used his combinations in flurries - even though only one punch in each flurry landed, Canelo did not respond."

Here we go.

Amir Khan looks twitchy as a bunny. Reflexes sharpened to a point.

Great combination from Khan. A left and quick right hand just bounce off Canelo though, who looks completely unaffected.

Canelo briefly has Khan cornered, but the Briton rolls the shoulder and slips free.

More slick punching from Khan. Canelo is taking the measure of his man and has not pinned him down yet.

I make that Khan's round and Virgil Hunter agrees. "We are one up," says Khan's trainer.

Image source, AP

Amir Khan is announced to the crowd. Who, with Mexicans in the vast majority, respond with jeers.

The ring announcer breaks into Spanish to welcome to Canelo and he gets a raucous reception.

The referee issues his final instructions.

A final look at the stats before they pass their expiry date...

Image source, Getty Images

Ben Dirs
BBC Sport at T-Mobile Arena, Las Vegas

"Khan looked very nervous during his ringwalk. Then again, wouldn't you?"

Canelo makes his way to the ring in almost subdued style.

He looks loose and limber, ready to do his thing.

His body language is the more eloquent when it comes to the subject of victory.

Amir Khan emerges into the Arena with trainer Virgil Hunter's hand on his shoulder as he guides him to the ring amid some Mexican bile and bouncing hip-hop.

He looks nervous. Can he channel that adrenaline into performance? Or will it freeze his muscles and leave him cold.

Ben Dirs
BBC Sport at T-Mobile Arena, Las Vegas

Eight screens above the ring, no excuse to miss a thing at the T-Mobile Arena...  

Amir Khan's final drill in his dressing room involves planting his feet and throwing big power punches at the pads.

He won't be trading like that come ring-time.

Here he comes...

William Davies: Here we go....can't see Khan winning. Out of his depth in this weight and companionship. But you never know. It's a funny old game.  

Jamal Ali Hayel: Khan is going to nick this fight.... mark my words.

James Paul Waterhouse: Khans goin down in the forth....not good enough 

Ben Dirs
BBC Sport at T-Mobile Arena, Las Vegas

"Khan roundly booed whenever he appears on the big screens, pretty obvious who the house fighter is..." 

The Republican presidential front runner won't be there. Not surprising as both fighters have thrown verbal punches at him., external

He is missing out.

A singer called Danny Walten belts out a elaborate, melodramatic version of God Save the Queen.

His Mexican equivalent does the same with his own country's tune.

The fighters are prowling backstage.

Paulie Malignaggi
Former welterweight world champion, speaking on BBC Radio 5 live

"Canelo is susceptible to frustration and Amir has the ability to frustrate the bigger boxer. It is about making the right decision at the right moment. 

Sometimes it is about throwing the punch, sometimes it is about stepping away and sometimes it is about a brief exchange before stepping away. It is about having that intelligence under pressure."