We study the decays of ultraheavy ( m _ { X } \geq 10 ^ { 13 } ~ { } GeV ) and quasistable ( lifetime \tau _ { X } much larger than the age of the Universe t _ { 0 } ) particles as the source of Ultra High Energy Cosmic Rays ( UHE CR ) .
These particles are assumed to constitute a tiny fraction \xi _ { X } of CDM in the Universe , with \xi _ { X } being the same in the halo of our Galaxy and in the intergalactic space .
The elementary-particle and cosmological scenarios for these particles are briefly outlined .
The UHE CR fluxes produced at the decays of X- particles are calculated .
The dominant contribution is given by fluxes of photons and nucleons from the halo of our Galaxy and thus they do not exibit the GZK cutoff .
The extragalactic components of UHE CR are suppressed by the smaller extragalactic density of X-particles and hence the cascade limit is relaxed .
We discuss the spectrum of produced Extensive Air Showers ( EAS ) and a signal from Virgo cluster as signatures of this model .