  It is proved that quasi-exactly soluble potentials (QESPs) corresponding to
an oscillator with harmonic, quartic and sextic terms, for which the $n+1$
lowest levels of a given parity can be determined exactly, may be approximated
by WKB equivalent potentials corresponding to deformed anharmonic oscillators
of SU$_q$(1,1) symmetry, which have been used for the description of
vibrational spectra of diatomic molecules. This connection allows for the
immediate approximate determination of all levels of the QESPs.
