Add SFTP password within a script

Question

I am working the following script , to export a backup file in a sftp server-

sftp  user@host <<EOF
<password>
cd /dir
put /tmp/backup'$(date +"%Y%m%d0300")'.tar.gz
bye
EOF

But it is still asking me password, could you tell me how to add sftp password inside a script? (without expect,sshpass)