  We propose new effective inter-nucleon forces with a finite-range three-body
operator. The proposed forces are suitable for describing the nuclear structure
properties over a wide mass number region, including the saturation point of
nuclear matter. The forces are applied to microscopic calculations of $Z=N$
($A\le 40$) nuclei and O isotopes with a method of antisymmetrized molecular
dynamics. We present the characteristics of the forces and discuss the
importance of the finite-range three-body term.
