What is the most difficult word to pronounce in the English language?

Two words, the combination does the trick. Purportedly posed by allied troops to Germans, camouflageing to be allied troops: 'Please say: several months'

With the intent to pronounce correctly this is supposed to become a stumblesome effort...

Well, this is just not true, "several months" is very easy one.

The most difficult word to pronounce correctly in English is:

ORDER