How to propage WebSphere security tokens when calling HTTP from EJB

I have an EJB which makes a call to another server in the cell using HTTP (REST api).

At the EJB context the user is already authenticated and authorized, how can I propagate the security tokens to the other server avoiding the need to provide credentials in the request ?

It is possible to obtain WebSphere's Ltpa token from the security subject and pass it as a cookie for the HTTP call:

public static SingleSignonToken getSSOTokenFromSubject(final Subject subject) {
    if (subject == null) {
        return null;
    }
    return AccessController.doPrivileged(new PrivilegedAction<SingleSignonToken>() {
        public SingleSignonToken run() {
            Set<SingleSignonToken> ssoTokens = subject.getPrivateCredentials(SingleSignonToken.class);
                for (SingleSignonToken ssoToken : ssoTokens) {
                if (ssoToken.getName().equals("LtpaToken")) {
                    return ssoToken;
                }
            }

            return null;
        }
    });
}

// Get cookie to add to outgoing HTTP requests
SingleSignonToken ssoToken =  getSSOTokenFromSubject(subject);

String ssoTokenStr = null;
if (ssoToken != null) {
    byte[] ssoTokenBytes = ssoToken.getBytes();
    ssoTokenStr = com.ibm.ws.util.Base64.encode(ssoTokenBytes);
}
String ssoTokenCookie = "LtpaToken2=" + ssoTokenStr;

By adding the ssoTokenCookie to the request cookies there is no need to provider user credentials.