issue facing with ansible-playbook, [UNREACHABLE]

[Modak, Prashant Kumar]

Hi,
I am facing an issue while i am trying to run the following command:
ansible-playbook -i inventories/standalone database.yml

(ENV) [js-170-53] xseduser 
~/Desktop/airavata/dev-tools/ansible-->ansible-playbook -i 
inventories/standalone database.yml

PLAY [api-orch] ****************************************************************

TASK [setup] *******************************************************************
fatal: [172.19.166.12]: UNREACHABLE! => {"changed": false, "msg": "Failed to 
connect to the host via ssh: Permission denied 
(publickey,gssapi-keyex,gssapi-with-mic,password).\r\n", "unreachable": true}
        to retry, use: --limit 
@/home/xseduser/Desktop/airavata/dev-tools/ansible/database.retry

PLAY RECAP *********************************************************************
172.19.166.12              : ok=0    changed=0    unreachable=1    failed=0

Please let me know if I am doing any wrong configuration setting or missing 
some configuration.

Thanks.
Prashant