You can put it in a crontab if you follow these steps:
Problem message: pavel@host's password:
Solution: make sure that your public key was added to the authorized_keys
file on the remote host, meaning make key based login at least working.
Problem message: Enter passphrase for key '/home/pavel/.ssh/id_rsa':
Solution: replace the password from the private key
The latter action of course introduces a lack of security, but there is no way around if you want to fully automate this.