Does the sponserer's immigration status matter for visitor visa?

[hshah]

Hi,
I am planning to sponser my sister and her family.
I am currently green card holder and will be US citizen by end of the month (Have passed the citizenship interview but has not taken oath, so I am still not US citizen).
I am thinking to send them sponsership papers but I am confused as to when should I send them the papers?
Before I become the US citizen or after I become a US citizen.
Has anyone any idea/thoughts on this ?
Thanks.

[Murali]

Any time, it is recommended to send close to their interview date.
Your immigrant status wont have any impact on this process.