SharePoint authentication from Siteminder authenticated portal

Hello Techies,

We have intranet portal which is authentication using Siteminder against AD. There is search textbox and submit button on portal. Upon entering search terms and clicking on Submit button, we want to redirect users to SharePoint searchresults page with k=searchterms.

The major hurdle is, SharePoint is AD authenticated so when users are redirected we don't want to show them AD authentication popup again as they are already authenticated by Siteminder.

Is there any way we can pass-in User context from portal to SharePoint so that SharePoint does not ask for authentication again?

Thanks,

SF...