Ajax post from a mobile app

Hi, I'm a trying to create a user using Ajax from a mobile app with javascript and I'm struggling!!!

Here is what I'm trying: user = {username:'plop', password:'plip', password_confirmation:'plip'}; new Ajax.Updater('all', HOST + 'users/create',{   method: 'POST',   parameters:{'user': user} });

When I look at the log It seems that is doesn't recognize first that is a POST method and it doesn't recognize my user parameter.

Here is the log: Processing UsersController#create (for 127.0.0.1 at 2010-06-04 20:40:07) [OPTIONS]   Parameters: {"action"=>"create", "controller"=>"users"}

Here is how it should be: Processing UsersController#create (for 127.0.0.1 at 2010-06-04 20:35:46) [POST]   Parameters: {"commit"=>"Submit", "action"=>"create", "authenticity_token"=>"/fkA8CQVp88xDB1Tbf/T2OHldbpc0QQlsBk7yk/7mxA=", "controller"=>"users", "user"=>{"password_confirmation"=>"[FILTERED]", "username"=>"toto", "password"=>"[FILTERED]"}}

Greg