Promoter Eddie Hearn has pledged to fight tooth and nail for Kell Brook as confusion surrounds his world title bid.

Sheffield boxer Brook was due to face Devon Alexander for the IBF belt in Detroit on 23 February but the latter withdrew on Monday citing a bicep injury, a second postponement after Brook had cancelled their 19 January date with an ankle problem.

The situation became more tangled this morning when Floyd Mayweather Jr, the unbeaten pound-for-pound best fighter in the world, said he was close to signing a deal with Alexander.

Writing on his official Facebook and Twitter pages, the 43-0 35-year-old said: "The negotiations for my fight are almost done. The front runner is IBF Champion Devon Alexander. It'd be a unification bout at welterweight."

As Brook is the mandatory challenger to the IBF belt Alexander won against Randall Bailey last year, negotiations would not be as straightforward as Mayweather makes out.

With the the Brook-Alexander fight due to have been in just 17 days' time, contracts had been signed and tickets sold, so Hearn is keen to find out what is going on.

Writing on Twitter himself, the Matchroom boss said: "My thoughts on the @SpecialKBrook\Mayweather\Alexander situation. Number 1 we have a signed contract to fight Devon Alexander for the IBF Title.

"Number 2 If they want Alexander v Mayweather to be a unification they would have to ask for an exemption from the IBF which is very unlikely given we already have signed contracts AND any exemption would have to take place within 90 days of last bout."

He then went on to question Golden Boy Promotions - Alexander's team - about their involvement, especially in light of last year's announcement that they plan to start staging shows in England.

Hearn wrote: "We questioned the injury and now we await news from @GoldenBoy Boxing which, given the news they are looking to enter the UK promoting market, should be interesting.

"We will fight tooth and nail for @SpecialKBrook and thanks for your support. More news soon."

There was no comment from either Golden Boy or the IBF when asked by Press Association Sport, although the former were still running a 4 February story on their official website which said a new date was being arrange for Alexander-Brook.

Mayweather, for whom any fight will be his first since being released from prison, is thought to be lining up a 4 May show in Las Vegas.