rsync via multiple ssh connections with a key

I need to do a rsync from a target server with a server in the middle and I have the same public key on both the target and middle server. I want to use that key so I don't have to do password authentication.

local --ssh--> middle --ssh--> target

Reading Method 1 of Using rsync through a firewall makes it seems like this is doable but I have been able to figure out the ssh part of the syntax of the command yet.

When I try

ssh -i $KEY -A user@middle ssh user@target

I get

Permission denied, please try again.
Permission denied, please try again.
Permission denied (publickey,password).

Clearly the agent forwarding isn't happening as I was expecting it to.

Ideally I'd like to fit it all in one command without have to put anything in ~/.ssh/config files. What are all of the steps to do an rsync in this situation?

Thanks, Everett

The '-A' will only "carry" identities loaded into ssh-agent. ('-i' on the command won't be enough.)

How about this something like this;

ssh-agent sh -c "ssh-add test_ident; rsync -avr --rsh='ssh -TA hostA ssh -TA ' foo/ hostB:/var/tmp/foo/"

Personally I do this in two hops with the following script:

#!/bin/bash
ssh -fN [email protected] -L2211:target.foo:22
rsync "-e ssh -p 2211" /Users/me/dir1/ root@localhost:/backup/dir1/ -avz --progress --delete-after
rsync "-e ssh -p 2211" /Users/me/dir2/ root@localhost:/backup/dir2/ -avz --progress --delete-after

mod as required.

It seemed easier than playing with the rsync options and if your target and middle have your key you shouldn't be prompted.