Need help finding max from 3d locfit output

Hi I am running the following locfit function:

fit <- locfit( log(base$Value) ~ base$lBrkOut +  base$lExit , alpha=0.9)
plot(fit,type="persp" )

The above two steps create a nice 3d plot. I would like to find the xy
coordinates where the maximum z occurs. 

Does any one know of function to call that will display the xy coordinates
where max(z) occurs?

Thanks
Lawrence