asterisk users - Feb 2005 - passing "*" into a dial plan

I'm trying to dial for example *67 to block caller ID but is it not
working.

I have SPA-3000 an dial plan:
exten => _9.,2,Dial(SIP/${EXTEN:1}@pstn-spa3k,60,tr)

If I try 
exten => _3.,2,Dial(SIP/*67${EXTEN:1}@pstn-spa3k,60,tr)

it gives me congestion.
How to pass "*" in a context when dialing a number?

-- 
#Joseph