Amir Khan has set Floyd Mayweather a five-day deadline as he attempts to line up a fight against the pound-for-pound king.
Khan has long been seeking the clash and enhanced his claims for a shot at the undefeated American with a convincing win over Devon Alexander in December.
The Bolton fighter had previously pulled out of a prospective fight against Alexander because he thought he had landed Mayweather only for the 37-year-old to chose Marcos Maidana as his opponent.
That came after Mayweather had asked fans on Twitter to vote on whether he should face Khan or Maidana, with Khan coming out the winner.
The 28-year-old defeated Luis Collazo on the undercard of that May 3 bout but then missed out again as the five-weight world champion decided to hand Maidana a rematch in September.
And with speculation mounting that Mayweather is close to agreeing a bout with Manny Pacquiao, Khan is keen to get a decision so he can begin preparations for a fight in May.
"I want to fight in May and I want the Mayweather fight but it's not getting any closer," he told the Daily Mail.
"I've answered all the things Mayweather wanted me to do. He wanted me to fight at welterweight, I did that; he wanted to do a vote, I won the vote; he wanted me to beat a top guy in the division and I gave Devon Alexander a beating he'd never had before.
"There is a lot of money in a fight with me, not just in America, but he's trying to avoid me. He's avoiding two names in boxing, Manny Pacquiao and AmirKhan.
"Mayweather wants to keep his '0', he doesn't want to take the big fights. If he's not fighting the top guys but is fighting guys who are over the hill or not at their peak, he's going to be undefeated.
"One thing about me is I've fought guys at their peak and who have been dangerous. I didn't have to fight them but I did. Losing doesn't make you a bad fighter, losing shows how good you are if you come back from those losses.
"It's a waiting game, I've given his team five days. I need to know this week because I need to start training."