It’s Liaise. Not Liase, no matter what Mr Gates’ spellchecker may tell you.

Useless fact for word buffs: “Liaison” is a seventeenth century cookery term and “liaise” was invented by the army in the 1920s. [words-work]

I have a friend who was once the editor of a major London listings and culture magazine. He once told me that as a matter of course, he binned every CV for an editorial position which spelled that word wrong. You might be able to use it in context, he argued, but if you rely on your computer to tell you when you’ve made a mistake, you won’t be terribly useful.

After he revealed that, I strangely became a lot more fastidious about checking.