U.S. vs. British English spelling question

[Eric Thomas]

Hi all.

I'm trying to ensure I'm spelling a word (or, more accurately, a family of
words) with U.S. English spelling as opposed to British English. The root
word is cancel. I know that in U.S. English the past tense is canceled.
However, I'm interested in the related noun "cancellation" - is it supposed
to be cancelation (with one "l") or cancellation (with two)? The
dictionaries I consulted were a little vague when it came to that particular
word.

Any suggestions? I want to be consistent (and hopefully correct as well).

Thanks.
-Eric