How to disable Reject Button from Worklist Notification from Isupplier Portal

Hello,

There is a requirement to not allow supplier "Reject" a Purchase order line during acknowledgement process via isupplier portal from worklist notification.

Any ideas on how to restrict/remove the "Reject" option at wroklist Notification.

What is the source LOV table for this field ?

Navigation: iSupplier responsibility --> Home Page ->Select PO --> Choose Acknowledge in Action then GO --> Show all details

Thanks in Advance!