Amir Khan has revealed he agreed to fight Saul Alvarez having watched footage of the Mexican and concluding he could win.

The 29-year-old will be a significant underdog when challenging the far bigger Alvarez at a catchweight of 155lbs for his WBC middleweight title after jumping two divisions, beyond welterweight.

He first received a text message from Golden Boy promoter Oscar De La Hoya about the potential fight on May 7 at Las Vegas' new 20,000 capacity T-Mobile Arena.

And only after studying the champion - who occasionally struggles with mobile opponents - did Khan believe he could succeed.

He told Press Association Sport: "I saw the videos and they gave me so much confidence I thought 'this is the right fight for now'. I saw him being slow, and being a big puncher (too), but for him to land he has to catch me.

"I spoke to Virgil (Hunter, Khan's trainer), and Virgil is the one who said to me 'look, if you're happy with the fight, it's a good fight for us'.

"He's been watching videos (of Alvarez) as well. What I have to do is stick to the gameplan. I can't make any mistakes or be a guy who loses focus because I can get hurt for that."

His trainer Virgil Hunter - widely respected for his work in guiding the masterful Andre Ward - has a reputation as a disciplinarian so it surprised many that he agreed to a fight few believe Khan will win.

But the 2004 Olympic silver medallist explained that Hunter needed persuading and also spoke of a belief his trainer could be his greatest asset come May.

"Yeah, he did (take persuading), but obviously he believes in me a lot," he said. "Virgil Hunter's the one who's going to be the biggest help in this fight."