Amir Khan has confirmed his fight with Lamont Peterson in Washington next month will be his last as a light-welterweight - unless he can tempt fellow unified champion Timothy Bradley into the ring.

Bradley - Khan's only serious challenger for the position of world number one at 140lbs - has shown little interest in a showdown with the Bolton star despite Khan's persistent attempts to lure him into the ring.

And Khan believes that if Bradley continues to refuse a big-money unification bout he will have no option but to shed his own light-welterweight belts and move up a division in search of bigger challenges.

Khan said: "If the Bradley fight is there for me I'll stay at 140lbs, but if not I'll move up to 147lbs. It's nothing to do with the making the weight, it's for the new challenge and motivation.

"I want to meet new fighters and that is what is going to drive me. We'll see what happens after this fight and whether Bradley is going to take the fight. If not I will move up to 147lbs."

Khan makes his debut in the US capital at the Convention Center on December 10 and he admitted he is relishing the prospect of taking on home favourite Peterson in another major American city.

Khan said: "I've got that style that people love - that speed, power and explosiveness - and I truly believe that although Peterson is the home town fighter, I will have more support than him on the night.

"They have not had a big boxing match in Washington for quite some time so it is great to be going there. I've always wanted to fight in different state capitals, so that everyone has the chance to see me live.

"I'm doing things the way they should be done. The best fighters in the world should fight the best fighters in the world. I wanted to fight Bradley and I fought Marcos Maidana and Zab Judah and beat them."