Deleting secret keys w/o public keys

[Michael Below]

Hi,

I have some secret keys in my secret keyring I don't have the
public keys for (these keys are old RSA keys, somehow remainders
from first tries with PGP). Now GPG gives me error messages like

gpg: key XXXXXXXX: secret key without public key - skipped

each time I encrypt or decrypt something.

Deleting the keys with --delete-secret-key or
 --delete-secret-and-public-key doesn't work, that leads to:

gpg: 0xXXXXXXXX: user not found
gpg: 0xXXXXXXXX: delete key failed: public key not found

How do I delete these keys?

Thanx for your help -- and please Cc: me, since I'm not subscribed
to this mailing list...

Michael Below