I've tried this and worked great without any prompts ...

it will still give you the warning message but wont ask anything ...

if you have access to both the servers and if u know the username on both the servers try this procedure

Source -- Howto Linux / UNIX setup SSH with DSA public key authentication (password less login)

(1)
System from where you will run the script

bash-3.00$ ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_dsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/user/.ssh/id_dsa.
Your public key has been saved in /home/user/.ssh/id_dsa.pub.
The key fingerprint is:
somenumbers user@server


(2)


Copy id_dsa.pub to the other system at the location as

~/home/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

(3)

Run this command on remote system

exec /usr/bin/ssh-agent $SHELL
Ssh-add

Then ,

you may cron the SCP script

use scp command as
"scp -o Port=22 (or wtever) source dest "
source could be /home/blah.txt
dest could be username@remote_Server:/home/asd

it worked great for me ...

Good Luck