Caching RJS fragments

Do you have any hint for using fragment caching within a RJS response?
I've the following piece of code in a rjs template

for hotel in @hotels
  cache(:id =>, :format => params[:format]) do
    page.insert_html(:bottom, :items, :partial => hotel, :locals =>
{ :city => @city, :country => @country })

but when the response is rendered it returns the following error,
probably because cache expects an ERB template.

ActionView::TemplateError (undefined local variable or method
`_erbout' for #<ActionView::Base:0x20b8e00>) on line #2 of hotels/

I searched the newsgroup and I read thousand of blog posts but I
haven't been able to figure out a reasonable solution.
Any suggestion?