How to approach and improve an employee's English skills?

I run a small IT development team. One of my employees does outstanding work, but is a little shy and reserved. I'm sure this has to do with his poor English skills. One-on-one, he's fine, but as soon as he has to present something or talk in a group, it seems that he gets a little flustered and he's hard to understand. It's workable, but things would go a lot easier for everyone if his English was better.

How do I encourage him to work on language skills without embarrassing him? I don't know how to approach the situation without coming off as insulting or demeaning. I want to help him succeed, but not sure the best way to accomplish this.