Boro's main targets at present are all midfielders and are under contract with their respective clubs. Chelsea's Steve Sidwell, Tom Huddlestone of Spurs, Newcastle's James Milner and Michael Bradley of Heerenveen are all being closely monitored by Southgate.
Asked by the Gazette how soon fans can expect to see new arrivals being unveiled at Rockliffe Park, Southgate said: "Difficult to say. There's no way of knowing.
"We've got targets. Everybody is finished now so they'll start to reflect on what they're needing to do but negotiations take time because selling clubs - the same as we would be - they'll want the best possible price and that means on occasions you have to wait for deals to be done."