NTBACKUP in W2003 and in W2K server

I try to use NTBACKUP command line in W2003 to make backup on DAT.
The command line is as follows (derived from the example of W2003 Help);

ntbackup backup "@C:\bks\Full.bks" /m normal /j "DataFull" /p "4mm DDS" /n
"Full" /d "Special" /v:yes /r:no /l:s /rs:no /hc:on

But the NTBACKUP utility aborts after the message "mounting media" before
execution of the backup.
Report shows "not found the specified media or backup device."

Actually I am using NTBACKUP command line in W2K server as follows;
ntbackup backup "@C:\bks\FullMain.bks" /J "FullMain" /d "FullMain" /v:yes
/rs:no /hc:on /m normal /p "4mm DDS" /UM

The command line works in W2K perfectly.
But this does not work in W2003 environment. Presumably /UM has no longer
been supported in W2003.

Any advice would be appreciated.

Simon