The 49-year-old enjoyed a break while the tournament was under way, although still managed to complete the signings of Cristian Riveros, Simon Mignolet and Ahmed Al-Muhammadi before his squad's return for pre-season training last week.
But now he is back and attempting to push home his interest in the club's remaining targets with Sol Campbell and Marcos Angeleri among his main priorities.
Bruce said: "Birmingham have done one or two bits, Man City have done one or two bits, but it has been very quiet.
"We have all watched the World Cup and basically had June off. It's starting now, by the phone calls we are having.
"Everybody is jostling for position and trying to get a few new bodies in, and I would think the work will start now.
"But I think there has been a reality check right throughout the football world. The recession has hit the football industry as well because there is not a lot of cash swilling around at the moment.
"We will see what develops over the next few weeks."
As well as arrivals, Bruce is expecting departures from the Stadium of Light with the likes of Nyron Nosworthy, Daryl Murphy, Marton Fulop, David Healy and Jean-Yves Mvoto, who were all sent out on loan last season, among those who could move on.
The manager said: "The four, five or six players we have had out on loan have come back, and I would envisage them looking to see if they can get themselves fixed up."
Striker Darren Bent has returned to training after being given extra time off following his trip to England's pre-World Cup camp, while Riveros and Paraguay team-mate Paulo da Silva will resume on July 27 following their exploits in South Africa.