how to make background of opengl window transparent

Hi,
I am making an opengles 2.0 application where i need to make the background of the window transparent and then show a blended object over it. Please can someone tell me how can i make window background transparent. The appearance i want is that it sud appear as if only a blended object is in front.
Any help will be greatly appreciated. Thanks in advance.
With regards,
Aditya

Just use glClearColor(r, g, b, 0.0f). Then there needs to be some blending happening external to the application window, either enabling source alpha blending on the layer, or source alpha blending on the window, managed by the windowing system.

Thanks for the reply… I am new to opengl. So please can u tell what did u mean by this statement. “there needs to be some blending happening external to the application window, either enabling source alpha blending on the layer” …Which layer are u talking about.
Or Do u i need to create a mini windowing system (window manager) of my own ??
Thanks in advance for the help.

Transparent windows need to be supported by the window system you are using. This is outside the scope of OpenGL ES.