tree() - Tree is too big

I am using tree() in the library tree to learn regression trees. Once in a
while I am getting the error "Tree is too big". From the same data set, but
with randomized subsets I am learning several tree model and in the end of
the day I would like to look at some of the properties across trees.

My problem: I have for loop containing a call to tree(). However, since
tree() returns an error about every 30-50 time due to "Tree is too big" the
execution is stopped. Since each call to tree() takes a long time I would
like to run the  for loop over night. I have tried

  options(error = expression(NULL))

to make [R] ignore the errors, but it seems that tree() doesn't respond to
this. Is this correct? Any other suggestions?