Transverse momentum event-by-event fluctuations are studied within the string-hadronic model of high energy nuclear collisions, LUCIAE. Data on non-statistical PT fluctuations in p+p interactions are reproduced. Fluctuations of similar magnitude are predicted for nucleus-nucleus collisions, in contradiction to the preliminary NA49 results. The introduction of a string clustering mechanism (Firecracker Model) leads to a further, significant increase of PT fluctuations for nucleus-nucleus collisions. Secondary hadronic interactions, as i...
