Try:
winscp.exe /console /command "open administrator:abcdefg01@99.99.99.99 -hostkey=""ssh-rsa 1024 9d:d9:e9:69:db:cf:9c:71:8d:cb:da:a5:cf:a7:41:a7
"" "put New.txt new.txt"

Howdy

I need to use the command line to sFTP a file, I tried to embed the -hostkey in the command, however, it seems the winSCP can not recognize it...

I ran
=====
D:>winscp.exe /console /command "open administrator:abcdefg01@99.99.99.99 -hostkey=/"ssh-rsa 1024 9d:d9:e9:69:db:cf:9c:71:8d:cb:da:a5:cf:a7:41:a7
/"" "put New.txt new.txt"

got
=====
Searching for host...
Connecting to host...
Authenticating...
The server's host key was not found in the cache. You have no guarantee that the
server is the computer you think it is.
The server's rsa2 key fingerprint is:
...............

Could you please advise what's wrong with the command I am using?

Thank you.