  Continuous variable entanglement is a manifestation of nonclassicality of
quantum states. In this paper we attempt to analyze whether and under which
conditions nonclassicality can be used as an entanglement criterion. We adopt
the well-accepted definition of nonclassicality in the form of lack of
well-defined positive Glauber Sudarshan P-function describing the state. After
demonstrating that the classicality of subsystems is not sufficient for the
nonclassicality of the overall state to be identifiable with entanglement, we
focus on Gaussian states and find specific local unitary transformations
required to arrive at this equivalency. This is followed by the analysis of
quantitative relation between nonclassicality and entanglement.
