ABSTRACT: We present a grand unified model based on the supersymmetric SU(3)L⊗SU(3)CL⊗SU(3)CR⊗SU(3)R gauge group, which unifies in one single step the three gauge couplings of the standard model at an scale M∼1018 GeV, and spontaneously breaks down to SU(3)c⊗U(1)EM using only fundamental representations of SU(3). In this model the proton decay is highly suppressed and the doublet-triplet problem is lessened. The see-saw mechanism for the neutrinos is readily implemented with the use of an extra tiny mass sterile neutral particle for each generation which provides a natural explanation to the neutrino puzzle.