processing results from INTERSECT, UNION or EXCEPT

I'd like to do something as follows

SELECT t1.id FROM t1 WHERE t1.id IN (SELECT t2.id FROM t2 INTERSECT
SELECT t3.id FROM t3)

i.e. use results from a set-operation.
If i do this in psql, i get an error message

ERROR: parser: parse error at or near "intersect"

Is there any way to do this besides using a temporary table?

Thanx,
  Jody