3498871 - "Could not reach test WS through specified SAP Web Dispatcher" error in SOLMAN_SETUP "Define HTTP Connectivity"

In 2.1 "Define HTTP Connectivity" page of SOLMAN_SETUP, when click on "Check URL" button of "Use SSL for Internal WS Access", the error will be displayed as below
Could not reach test WS through specified SAP Web Dispatcher: https://<SAP Web Dispatcher hostname>:<WDP HTTPS port>
Message No. CL_URLAPI_MESSAGE059

But when click on "Check URL" button of "URL (External Access)" with same SAP Web Dispatcher hostname & port, there is no issue, message like:
SAP Web Dispatcher for External Access: URL <SAP Web Dispatcher hostname>:<WDP HTTPS port> reached

As client, Solman system will establish SSL connection to SAP Web Dispatcher, in SRT_UTIL or ICM trace of Solman system, following errors can be observed:
[Thr xxxxxx] *** ERROR => SSL handshake with <SAP Web Dispatcher hostname>:<WDP HTTPS port> failed: SSSLERR_PEER_CERT_UNTRUSTED (-102)
[Thr xxxxxx] Peer's X.509 certificate (chain) validation failed (missing trust?)
[Thr xxxxxx]
[Thr xxxxxx]SapSSLSessionStartNB()==SSSLERR_PEER_CERT_UNTRUSTED
[Thr xxxxxx]   SSL:SSL_read() failed  
[Thr xxxxxx]   => "Failed to verify peer certificate. Peer not trusted."
[Thr xxxxxx]   SSL:SSL_get_state()==0x2131 "TLS read server certificate B"
[Thr xxxxxx]   SSL NI-hdl 285: local=xxx:<ICM port>  peer=xxx:<WDP HTTPS port>
[Thr xxxxxx]   acli SSL session PSE "/usr/sap/<Sloman SID>/<instance>/sec/SAPSSLX.pse" (load=xxx xx:xx:xx 2024, rcnt= 0) 

SAP Web Dispatcher

Could not reach test WS through specified SAP Web Dispatcher, Use SSL for Internal WS Access, URL (External Access), SSSLERR_PEER_CERT_UNTRUSTED , KBA , BC-CST-WDP , Web Dispatcher , SV-SMG-INS-CFG , Setup and Configuration of the Solution Manager system , BC-SEC-SSL , Secure Sockets Layer Protocol , Problem