Newly-promoted Birmingham are determined to strengthen their squad with chairman David Sullivan confirming the club are pursuing several players.
The club has already confirmed the signings of Scott Dann and Geovanny Espinoza and are set to officially welcome Christian Benitez as soon as he completes a medical and Sullivan says there is more to be done.
"Since last season finished, it's been non-stop," Sullivan told the Birmingham Mail.
"We're working all hours of the day, seven days a week.
"During the last four weeks or so, I've never worked as hard as I have done since I've been in football. Negotiations have been incredibly stressful. Just when you think you've got someone, it changes.
"Another club might come in and hijack it, like Wolves did with the Coventry City player (Scott Dann) - and we then had to hijack it back. The demands of clubs, and players and agents - especially those out of contract or free - are ridiculous.
"But if you keep saying 'no', then you don't have a team. So what do you do?"