The distance between BPS branes in string theory corresponds to a flat
direction in the effective potential. Small deviations from supersymmetry may
lead to a small uplifting of this flat direction and to brane inflation.
However, this scenario can work only if the BPS properties of the branes and
the corresponding flatness of the inflaton potential are preserved in the
theories with the stable volume compactification. We present an ``inflaton
trench'' mechanism that keeps the inflaton potential flat due to shift
symmetry, which is related to near BPS symmetry in our model.Comment: 12 pages, 2 figure