Symfony2: how to set the host/base url in CLI scripts

I'm currently writing a newsletter tool, and therefore have to generate absolute URLs in a CLI script which is called via cron.

Unfortunately the Symfony CLI command does not know anything about my host/base_url, so the router generates absolute URLs with a wrong base_url. It always uses http://localhost as base.

Is there a way to tell the router the correct base_url?

My code:

$this->container->get('router')->generate($route, $parameters, true);