Three sportswear giants are bidding to secure a world-record kit deal with Manchester United.
Adidas, Nike and Warrior remain in talks with the club over the right to take over when the existing agreement, with Nike, expires next season.
A figure of £600m over 10 years has been discussed, which would dwarf the reported £31m a season Adidas pays to Real Madrid.
United's existing deal with United States firm Nike is worth £24m a year.
Germany-based Adidas, who made United's kit throughout the 1980s, declined to comment but the BBC understands it is in talks with the club.
Nike and Warrior, the US company who manufacture Liverpool's kit, both confirmed to BBC Sport that they are also in the running.
|United sponsorship deals|
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A Nike spokesperson added: "United is one of the greatest clubs in the world and we're continuing discussions with them."
Puma, who sponsor Arsenal, declined to comment but are not thought to be among the frontrunners.
As part of the terms of their existing deal with United, Nike were granted a period of exclusivity to negotiate an extension, but that expired without a new agreement having been reached.
That opened the door for other companies to bid.
Nike, who are due to release United's new kit in the next few weeks and have been the Premier League club's partners since 2002, retain the right to match any other offer.
United, who tour America later this month, declined to comment.
They have signed a number of sponsorship deals, including a £120m agreement to rename their Carrington training ground.