How could open the url in muse with emacs-w3m?

Links such as "http://www.emacswiki.org" in muse is opened by
'htmlview'(firefox).
I want to open this links within 'emacs-w3m'.

I found the function,
(defun muse-html-browse-file (file)
(browse-url (concat "file:" file)))

So I add following function into the ~/.emacs file.

(defun muse-html-browse-file (file)
(w3m-browse-url (concat "file:" file)))

It is possible to open the published files(html) with 'emacs-w3m'. But I
cannot open
web links with 'emacs-w3m'

How could I do this?

Thanks.