Access session data from another thread

I have a issue here. In my web app i have a page that starts another thread for time consuming task. In this new thread i have a call to one of my architecture methods (Inside another project – an architecture project). The problem is: in one of this methods i access a HttpContext.Current.Session field. But when i launch the application a exception is thrown saying that this object (HttpContext.Current.Session) has a null reference. How could i set the context of the new thread the same as HttpApplication context in order to access HttpContext.Current.Session ?