Amir Khan has declared himself happy to undergo any drug test required to ensure he can fight Floyd Mayweather. Khan, who became unified world light-welterweight champion at the weekend by adding Zab Judah's IBF title to his WBA belt in Las Vegas, has his sights set on a showdown with Mayweather next year after he steps up to the 147-pound division.

The 34-year-old American has made it clear that any opponent must consent to his stringent drug-testing demands, something that has already proved a stumbling block in negotiations for a clash with Manny Pacquiao.

Last week Mayweather's uncle and trainer Roger accused Khan of taking steroids, but the Bolton fighter is not concerned by the allegations - which he strenuously denies - or the prospect of any testing procedure.

"I am a clean fighter - I get drug-tested in between, before and after fights," Khan, who won an Olympic silver medal aged 17 in 2004, told Press Association Sport.

"Whatever test he wants me to do, I'm happy to do it. When you see a fighter being very successful, I think people just want to put the fighter down and I think they were doing that by saying I was on steroids. I've never taken drugs in my life and never will, so that is why I am so keen on taking a test.

"I think they just want to break down fighters and get right into their heads. With me, it just doesn't work - I've been in the game getting drug tested since I was an Olympic athlete, so I don't think it will ever affect me.

"It gets petty when they talk about things like that, but (trainer) Freddie (Roach) and I are happy for me to take a drug test whenever."

Asked about his relationship with Mayweather, Khan said: "I've met him once or twice and we get on quite well, but I think when you are facing someone or fighting them, that respect kind of disappears.

"I think if I see him now, because he is a future opponent, it will be a little bit different."