I hope by now you guys would have got it done but still posting this solution so that other people can be benefited.
Please look in to the solution and correct it if i it is wrong.
For SSO using SAML token there are following things which are necessary.
–>> your web application server should also support SAML assertion and both of the systems (MWS and web application server) should use same directory server for authenticating user.
you need to follow below mentioned steps if above mentioned condition satisfied.
In your portlet binding view click on ‘Expert Properties’ then go to webservice which your portlet will be accessing at runtime. Select the ‘authentication method’ inside ‘authentication info’ from the property view choose the authentication method as SAML. Save and deploy your portlet to MWS.
Configure following SAML url in your web server.
after above mentioned configuration SSO should work.