Suppress "Are you sure you want to use this public key [y/N]?" in PGP (v6.5.8)

When I encode a given file with PGP v6.5.8 by the following command line command

pgp -ew filename pubkeyid

Then ALWAYS a question appears:

Are you sure you want to use this public key [y/N]?

How can I avoid this confirmation?
Is there a quiet flag (under WinXP) ?

Rod