Changing LaTeX files extension

Hello, 

I want to give may LaTeX files the extension .latex instead of the actual .tex,
I want to caracterize my Plain TeX files. 

In my .emacs file I inserted

(setq auto-mode-alist
       (cons '("\\.latex$" . tex-mode)
             auto-mode-alist))
 
but when I try to compile such a file, I have the following error

=====================================================================================================
Running `LaTeX' on `Etude_001.latex' with ``latex --src-specials
\nonstopmode\input{test.latex.tex}''
This is TeX, Version 3.14159 (MiKTeX 2.2)
LaTeX2e <2001/06/01>
Babel <v3.7h> and hyphenation patterns for english, french, german, ngerman, du
mylang, nohyphenation, loaded.


! LaTeX Error: File `test.latex.tex' not found.
=====================================================================================================


the extension .tex is added to the name of the file and of course the file
doesn't exist,
and I don't to prevent AUCTeX to add this extension.

My test.latex file :

=================================================================
\documentclass[leqno,a4paper]{article}
\usepackage[frenchb]{babel}

\begin{document}

Hello !

\end{document}


%%% Local Variables: 
%%% mode: latex
%%% TeX-master: t
%%% End:  
==================================================================

Does somebody know how to solve this ?

Thanks
Santi MAURO