Ice grains bond together in less than 1 s. The tensile strength of the resulting bond was measured above -25 ºC in the contact time range of 10-1000 ms as a function of temperature and contact load. The bond strength increases nonlinearly with time and with increasing temperature. The results indicate that the most likely mechanism of ice sintering on this time scale is the freezing of the liquidlike layer present on the surface of the ice. A model based on the plastic behavior of ice and the complete freezing of the entire contact patch well describes the observations.