how to delete a file from a tar?

[Suneal K. Chaudhary]

I've been using the Sun floppy disk drive as according to the
manual, and ive made a few floppies with tar.  But now i
want to know how to delete files from the tar without unpacking
the tar totally and then repacking it.  Im on a 
sparcstation 1+, and im using 1.44mb floppies.  i use
the device /dev/rfd0 (i think).  thanks in advance.