How to specify the private SSH-key to use when executing git pull?

Question

I need to do a git pull specifying the private key, like:

git pull [email protected]:User/Repository.git -key "~/git_key"

I know that I can set the key on "~/.ssh/authorized_keys", but I don't want to set the key global, only to specify the key on the git command.

Is it possible to do?

Thanks