  Given a virtual link diagram $D$, we define its unknotting index $U(D)$ to be
minimum among $(m, n)$ tuples, where $m$ stands for the number of crossings
virtualized and $n$ stands for the number of classical crossing changes, to
obtain a trivial link diagram. By using span of a diagram and linking number of
a diagram we provide a lower bound for unknotting index of a virtual link. Then
using warping degree of a diagram, we obtain an upper bound. Both these bounds
are applied to find unknotting index for virtual links obtained from pretzel
links by virtualizing some crossings
