Consuming SP Lists Web Service (SP 2010) from SP 2007 Web Part

Hello,

We have Sharepoint 2007 environment for Internet and Sharepoint 2010 for our Intranet. I am writing a webpart in SP 2007 that needs items from SP2010 environment. So how do i consume a Sharepoint 2010 Lists web service, mainly to handle authentication part ?(site has been configured with Claims based Authentication and authtype as integrated windows as well as Forms based authentication - I do not want to use FBA to get list items)

Thanks