Problem using libreoffice convert-to headless with Excel XML

I am trying to convert a file from Excels Spreadsheet XML format “XML Spreadsheet 2003” to Excel xls format using

“soffice --headless --convert-to xls filename.xml”

on a linux CentOS machine (without X11), but the converted file seems to be destroyed. When I open the converted file it only contains hieroglyphs.
Opening the original XML file on my Windows Libreoffice application works fine.