Error while cancel the Blanket release by calling API(po_document_control_pub).

Hi All,

I'm calling  an API(po_document_control_pub) to cancel the blanket release which was created based on dropship order ,I'm getting following error.

The Return Status of the API is => E
The Purchase Order Failed to cancel Due To Following Reason
The specified control action (Action = CANCEL) is invalid for this document.

Please help me how to resolve the issue.

po_document_control_pub.control_document(p_api_version => L_API_VERSION_NUMBER, p_init_msg_list =>L_INIT_MSG_LIST, p_commit => L_COMMIT, x_return_status =>G_RETURN_STATUS, p_doc_type => RELEASE, p_doc_subtype =>BLANKET, p_doc_id =>