  We study the effects of a repulsive three-body interaction on a system of
trapped ultra-cold atoms in a Bose-Einstein condensed state. The corresponding
$s-$wave non-linear Schr\"{o}dinger equation is solved numerically and also by
a variational approach. A first-order liquid-gas phase transition is observed
for the condensed state up to a critical strength of the effective three-body
force.
