LONDON: Amir Khan says he didn't want to demand a rehydration clause for his forthcoming fight with Saul Alvarez because he wants to make the biggest possible statement in his first bout above welterweight.

Former world champion Khan will fight above welterweight for the first time in his career at a catchweight of 155lbs, officially middleweight, to challenge Alvarez for the Mexican's WBC title in Las Vegas on May 7.

Given the significant difference in size between challenger and champion when they appeared together in London, it appeared a risky oversight that Khan did not demand a restriction on Alvarez's weight on fight night.

Alvarez's frame means there is little to stop him gaining a further 20lbs after weighing in to effectively compete at light-heavyweight and therefore leaving Khan, the underdog who turned professional as a lightweight, at an even greater disadvantage.

However, the catchweight limit is only a pound over light-middleweight and fully five pounds below the official middleweight limit, meaning it's practically a light-middleweight fight, which is the next division above Khan's welterweight category.

Alvarez has operated at light-middleweight for most of his career but won the WBC title against Puerto Rican Miguel Cotto when two light-middleweights fought at the same 155lbs catchweight for a middleweight belt.

Khan's best chance comes in using his superior speed and mobility, but he still maintained he hadn't taken an unnecessary risk with the weight issue.

“I wanted to do everything naturally because when I beat him I wanted to beat him fair and square and I don't want people thinking 'he was too dehydrated, he was too small, he couldn't put weight on',” said Khan, who hasn't fought since beating Chris Algieri in May last year.

“I want to beat the best Alvarez, fight the best Alvarez. The fights I've been watching he was really hydrated, and normal, where he was happy making the weight.

“Yeah [we considered a clause], I spoke to Virgil [Hunter, my 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 game-plan. I can't make any mistakes or be a guy who loses focus or makes mistakes because I can get hurt for that.”