Chris Coleman says he wants most of Sunderland's signings done and dusted before the club return for pre-season in late June.
It is set to be another summer of extraordinarily high turnover at the Stadium of Light, with seven loanees returning to their parent clubs and a number of players out of contract.
Martin Bain said on Tuesday that around 14 players are likely to be needed to bolster the ranks, but uncertainty over the club's ownership continues to hamper attempts to recruit.
Coleman said: "We know we are in League One now, and it's not a case of consolidating – it's not that at all.
"We have got to win promotion, it doesn't matter how we do it, we have to win promotion and get some momentum.
"We need to build a certain type of team and to do that we need the green light from the right people.
"If that doesn't happen, this transfer window will come and go.
"People will think that we have time, but we don't have time.
"We need to start working right now, so that when we come back for pre-season we have the majority of our signings in place, with maybe just one or two more to come.
"We need to start now. Every 24 hours that goes past is 24 hours we have lost."
Bain and Coleman have begun the process of contacting free agents who will be available this summer.