Anthony Joshua considers American Jarrell Miller or Alexander Povetkin of Russia his likeliest next challenger.
The IBF, WBA, IBO and WBO heavyweight champion's management have made an offer to Deontay Wilder, who holds the WBC title, for what would be the world's richest and most significant fight, but Joshua is not convinced of his interest.
Those working with Wilder most recently spoke of making a counter offer because of their dissatisfaction at the one made to them, which has contributed to Joshua's pessimism.
It is understood a fight with Miller, in New York on August 25, is one potential alternative, while the WBA recently demanded he make a mandatory defence against Povetkin.
Miller also first needs to defeat Johann Duhaupas on April 28, but asked whom he was most likely to fight next, Joshua said: 'Miller or Povetkin. If I was to list which (negotiations) would be easiest I'd put them at the start.
'Miller's more serious. Miller would definitely step up to the challenge. When these guys haven't got much to lose they're more serious, they know they've got everything to gain.
'Miller's a bit more serious because it seems he hasn't got as much to lose, he'll jump at the opportunity. If Wilder was as serious as he says he is he would jump at the opportunity.
'I haven't heard from the president of the WBA, but that's a conversation to be had. If there was a situation where Wilder accepted the challenge and it was something he was looking to do this year, it would be a conversation with the WBA, to see how we could hopefully postpone Povetkin until 2019. I didn't work this hard to give things away.
'Wilder's had 40 fights. The fans and broadcasters are fed up so he has to make a move. That fight will happen sometime.
'My career isn't based around Wilder - that's what's clear about it.'