Converting FTP script to SFTP

The code below allows me to log into an FTP server decide which directory I want and delete some files.
Please could you enable it to work on an SFTP server?

Set HostName=xx
set USERID=xx
set PWD=xx
set ScriptDir=xx
set FTPSCRIPT=%ScriptDir%\$tempftp$.$$$

echo open %HOSTNAME%>%FTPSCRIPT%
echo user %USERID% %PWD%>>%FTPSCRIPT%
echo cd newdirectory\subdirectory

echo mdel *.*>>%FTPSCRIPT%


echo bye >>%FTPSCRIPT%
ftp -i -n -s:%FTPSCRIPT%

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