Single Signon for WPF, WCF using WIF

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WPF

Hi,
I am working on WPF application. I am using claims based authentication using windows identity foundation. I created custom STS service for that. My WPF app communicates 3 WCF services(Relying parties).When I created wcf service proxy and sends requests, it first gets the security token from STS service and gets authorize to serve the request. Each wcf service proxy gets the security token from custom STS service and processed the requests. My WPF app is working fine. My 3 WCF services using same STS service and same certificate. Is there any way to use one wcf service proxy security token for another wcf proxy security token without communicate with STS service from WPF app?