Loading an external swf with a determined scale

programming flash
1

Hi guys, I’m new to as3 and i’m trying to load an external swf (as2) and I want to use it as a background for my movie.

I’m doing it with this code:

var bg = new Loader();
bg.load(new URLRequest("background.swf"));
addChild(bg);
bg.x = 0;
bg.y = 0;
bg.scaleX = stage.stageWidth;
bg.scaleY = stage.stageHeight;

Why is not working when I set as the width and height the stageWidth and stageHeight parameters?

Thanks