  In sterile neutrino (3+1) parameterisation, we observe that sterile phases
($\delta_{14},\delta_{24}$) are always together in oscillation probability,
even when the MSW effect is considered. We see that the difference between the
sterile phases has a more dominating effect over event rates compared to small
variations due to changes in individual values. In this work, we show the value
of sterile phase difference ($\delta_{14}-\delta_{24}$) that least affects the
parameter degeneracy resolution of $\delta_{13},\theta_{23}$ at long-baseline
experiments.
