Robert Page has suggested sending the Prince of Wales a bucket hat to win his World Cup support when they play England.
William has been president of the Football Association since May 2006 and regularly attends England matches.
But the newly-created Prince of Wales now has divided loyalties, with the two home nations drawn in the same World Cup group in Qatar.
Wales and England meet in Group B’s final fixture at Doha’s Ahmad bin Ali Stadium on November 29.
Asked if he could convert William in to a Wales supporter in time for the World Cup, manager Page replied: “Absolutely. Who’s he going to support?
“We’ll have to send him a bucket hat, eh?”
The bucket hat has become the must-have accessory for Wales fans over the past decade.
The yellow, green and red hats are worn in their thousands by the so-called ‘Red Wall’.
Players-turned-pundits Ashley Williams and Danny Gabbidon both wore bucket hats on television to celebrate Wales’ World Cup play-off final victory over Ukraine in June.