Problem with SSH

Hello,
i have 10 machines, machine A execute this script:
This is my script:

nb_lignes=`wc -l $1 | cut -d " " -f1`
 for i in $(seq $(($nb_lignes - 1)) )
 do
 machine=`head $1 -n $i | tail -1`
 machine1=`head $1 -n $nb_lignes | tail -1`
 ssh  root@$machine -x " scp /home/file.txt root@$machine1:/home && rm -r /home/file.txt"
 done

Please i have this error at run:

Host key verification failed. lost connection 

have you an idea please ?

Thank you so much.

Try to use this

nb_lignes=`wc -l $1 | cut -d " " -f1`
for i in $(seq $(($nb_lignes - 1)) )
do
machine=`head $1 -n $i | tail -1`
machine1=`head $1 -n $nb_lignes | tail -1`
ssh -x root@$machine  " scp /home/file.txt root@$machine1:/home && rm -r /home/file.txt"
done

What's the difference please between :

ssh root@$machine -x " scp /home/file.txt root@$machine1:/home && rm -r /home/file.txt"

and

ssh -x root@$machine  " scp /home/file.txt root@$machine1:/home && rm -r /home/file.txt"

Thank you so much

????????????

But i have tested ssh root@$machine -x with other command and it works correctly!!

Yups.. It will work..

Are you sure this is the cause of the error ?
i'm not connected now to the machines , i'will test it tomorrow
but i think this is not the cause.. I am not convinced...

Am not sure about it.. Let me to check and find the right one!!