Brentford are determined to keep Ollie Watkins next month and have increased their valuation of the forward.
The Bees believe they have the best chance since 2015 to reach the Championship play-offs and are considering entering the January market themselves in an attempt to boost their promotion push.
Sheffield United and Crystal Palace have shown an interest in Watkins and are expected to make approaches when the transfer window reopens.
But Brentford, currently fourth in the table, have increased the asking price beyond the £20m they were previously demanding.
Watkins, who was converted into a central striker following the summer sale of Neal Maupay to Brighton, signed a new four-year contract at Griffin Park in August.
He told West London Sport earlier this season that he had put the disappointment of not securing a Premier League move behind him and embraced his new striker role under boss Thomas Frank.
Watkins has scored 13 goals so far this season, taking his tally to 35 in 116 appearances since joining from Exeter in 2017.
Turkey youth international Halil Dervisoglu will join the Bees on 1 January, having agreed a move in the summer.
And the club are still considering trying to sign another striker in January.