Re-use a random forest with R

Re-use a random forest with R

I'd like to know if it's possible to re-use the rules of a random forest,
on different test set.
For now, I'm using this :
rf <-randomForest(x=train,y=labels_train,xtest=test, ytest=labels_test,
ntree=1000)
save(rf,file = "rf_.RData")
I know how to save the random forest, but I don't see how I can re-use the
rules, for several test set.