Submit form using link_to in rails

I'm trying to submit a form using link_to as follows: <%= form_for(@post, :url=> '/post/action', :method=> 'post', :html => {:id=>'form_id'} ) do |f| %> .... <%= link_to 'submit', "/post/action", :onclick=>"document.getElementById('form_id').submit()" %> .... but it is not posting the form, it is simply redirecting my form to the specified url. Does anyone know how to do this?