An unusually high-peak-temperature desorption state of O-2 from Pt{110} (1x2) has been characterized in temperature programmed desorption spectra after O-2 adsorption from a supersonic beam at a translational energy of 190 meV and at nozzle temperatures, T-n, greater than 870 K. It shows the characteristics of a subsurface atomic state of oxygen. From the nozzle temperature dependence of the rate of population of this state we conclude that it is formed exclusively from electronically excited O-2 (1)Delta(g) generated in the molecular beam source.