Anthony Joshua considers American Jarrell Miller or Alexander Povetkin of Russia his likeliest next challenger.
The IBF, WBA 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.
Press Association Sport understands 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 told Press Association Sport: "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."
It was on Thursday announced that the 28-year-old Joshua's biggest domestic rival, Tyson Fury, will return to the ring at the Manchester Arena on June 9 after agreeing promotional terms with Frank Warren.
Joshua, speaking at a Stubhub event, said of Fury's claim he remains the world's leading heavyweight: "If he wants to fight me next, he can fight me next. If he wants to fight 10 fights down the line, he can do that as well.
"It'll be a situation that, when the opportunity does come, he'll be saying he's the man who beat the man, he deserves this, he deserves that, and then he won't fight me.
"I'm the flag-bearer, the best heavyweight champion out there now. The ones who are scared to step up talk a good game, but don't really back it up so I get bored of it.
"When Tyson Fury's ready, we'll make it big, we'll make it fun. When Wilder's ready we'll make it big, we'll make it fun.
"With or without Fury my career will go on, with or without Wilder my career will go on, with or without Povetkin and the WBA belt my career will go on.
"I'll keep on doing this for another 10 years, and then I'm done."
- StubHub presents 'An Evening with Anthony Joshua', with all proceeds from tickets sold going to Steel Warriors. Buy and sell tickets via stubhub.co.uk