Aberdeen have reportedly told Celtic that they must improve their offer for Jonny Hayes if they want to remain in the race for the winger.
Celtic are looking to improve their squad after a history-making campaign in Scotland's top flight last season, but it appears that they face a fight to sign the 29-year-old.
According to the Press & Journal, Cardiff City have moved into pole position to sign Hayes after they made a £1.2m bid for his signature.
Celtic had been considered favourites to sign the Republic of Ireland international, but it has been suggested that Aberdeen will not entertain a deal which also includes the loan of Ryan Christie, who spent the second half of the season on loan at Pittodrie.
Last season, both Christie and Hayes played a key role in Aberdeen finishing in second place above Rangers, with Hayes contributing nine goals from 33 outings.
He has admitted that he is flattered by the interest shown in him by the Glasgow giants.
