Disk or partition space is insufficient

[admin]

I followed
"How to use WinToUSB to clone Windows 10 to an external hard drive as portable Windows 10"

System partition 200MB Fat32
boot partition NTFT of over 200 GB
Trying to clone a 100GB installed OS
Used an external SanDisk USB3 SSD drive of 250GB

Also Tried with a 500GB usb external disk and got the same error, so it looks the the size is not the issue

Log included

WinToUSB need to write a very small file (about 1 KB) to the system partition of the original Windows OS before WinToUSB cloning Windows to a USB drive. Unfortunately, your Windows system partition has no space to create this file. In this case, you need to delete some files from the system partition to get enough space.

Reference:

What are system partitions and boot partitions:
http://www.easyuefi.com/wintousb/faq/en_...tions.html