Rename Approve, Reject button in UWL Portal

Hi Expert

We have a requirment- user want to rename the "Approve, Reject" button in UWL approve page. The buttons should be:

1. Confirm to requester - For Approve button
2. Cancel and keep - For Reject Button (Same as in Tcode SBWP).

Please let me know from where should I modify it. Is it UWL XML file or anyother place at Backend. I have attached portal and workflow button screen shot for your ready reference. it is very urgent issue.

Regards

Keshari