In this paper, we construct a
splitting of the metaplectic cover of the reductive dual pairs of orthogonal
and symplectic groups or the reductive dual pairs of unitary groups over a
nonarchimedean local field with respect to a generalized lattice model of the Weil
representation. We also prove a result concerning the splitting that we construct and
the theta dichotomy for unitary group. The splitting plays a very crucial role
in the study of theta correspondence for p-adic and finite reductive dual
pairs.