Interop with Windows Identity Foundation STS for SSO

This is a SSO question - I have a Java Web app that needs to authicate against a Windows Identify Foundation-based STS. The relying party needs to issue a STR in an Http GET to the STS. The STS uses the WS-Federation Passive Requestor Profile. The STS will return a RSTR reponse with an encrypted SAML token that contains the principal and claims information.

I have no idea how to achieve this...

Is Metro the suitable framework for this? If so, what do I need to do? The exmaples and tutorials I looked at are all in relation to web service calls.

Any help is appreciated.

Thanks!