Can you convert to Roth 401k?

I'm guessing the answer is "no", but let's say you have money in a 401k with your current employer, and then the employer starts to offer a Roth 401k option as well. Can you pay income tax on what's in your 401k and convert it to Roth, or can you only contribute new money to the Roth 401k, and have to wait until you separate from your employer to rollover/convert the tax deferred 401k money?

Thanks

I don't think it is possible. Still waiting for others to response.

Domingo3,

I am with Plannerinus on this....

But I would check the 401k Summary Plan regarding contributions to your account.

Also ask the 401k custodian.
If this is possible, it would most likely be plan specific.

Let us know what you learn....

This is a somewhat hypothetical question. Best guess is that Roth option will come in 2010. I was asking because if you can't do a conversion, I may reduce tax deferred contributions for 2009 (and temporarily invest the difference in a taxable account) and then max out for 2010 into Roth.
I'll let you know when/if I find something out, but it will probably be a year from now.

Thanks