ATG has seen pitches from Harvard PR, Fuse PR and start-up Tannissan Mae and plans to hire one of them by the end of next week.
ATG's marketing manager for Western Europe Laura Parkinson said: 'This is a closed shortlist and we have narrowed it down to those three firms'.
ATG formerly retained Gnash Communications, which closed down in January (PRWeek, 31 January), causing the repitch.
Parkinson said the agency would seek to raise awareness of the ATG with IT decision-makers in companies with annual turnover of more than £100m.
It would target customer services and 'customer interaction' managers, plus 'vertical' publications such as financial and retail titles.
ATG, which stands for Art Technology Group, was set up in Cambridge, Massachusetts, in 1991.