We calculate, in a hydrodynamic approach, the m_T spectra of kaons in central Pb+Pb (Au+Au) collisions, as function of energy. The experimentally observed anomalous behavior of the inverse slope parameter T^* may be reproduced by a reasonable choice of the critical temperature T_c\sim 160 MeV at \mu =0 and an equally reasonable choice of energy-dependent freeze-out temperature T_fo, thus supporting the argument that these data are an additional signature of deconfinement transition. \relax

PACS numbers: 12.38.Mh, 24.10.Nz, 25.75.-q, 25.75.Nq