Chelsea are reportedly still some way short of Bayer Leverkusen's asking price for midfielder Kai Havertz.
The 21-year-old is thought to be keen on a move to Stamford Bridge too, and Chelsea were given the green light to step up their pursuit after the Bundesliga outfit were eliminated from the Europa League earlier this week.
However, Sky Sports News reports that the fee is proving to be a sticking point in negotiations, with Leverkusen holding out for £90m.
Chelsea, meanwhile, are hoping to strike a deal worth closer to £70m, which would take their summer spending to more than £150m already.
Frank Lampard is also thought to be in a market for a new left-back and goalkeeper during the ongoing window and so is eager to keep as much money left over for those targets too.