  The effect of nonmagnetic disorder on the pairing amplitude is studied by
means of a perturbation method. Using an extended one band Hubbard model with
an intersite attraction we analyze various solutions of p-wave pairing symmetry
and discuss their instability calculating fluctuations of order parameter. The
model is applied to describe the effect of disorder in Sr2RuO4. The results
shows that the real solution with line nodes can be favoured by disorder.
