CREATE TABLE SELECT, ON DUPLICATE KEY UPDATE, and UNION

[phillip.s.powell]

[SQL]
CREATE TABLE /*! IF NOT EXISTS */ blah
SELECT * FROM blah1 ON DUPLICATE KEY UPDATE unique_key=uniq ue_key
UNION
SELECT * FROM blah2 ON DUPLICATE KEY UPDATE unique_key=uniq ue_key
TYPE=MyISAM
[/SQL]

This transaction produces a syntax error

Syntax error near "ON DUPLICATE KEY UPDATE unique_'"

My task is to conjoin 2 tables together into one table with unique rows
from 2 tables with "duplicates " (rows that have identical values in
"unique_key " that should not be the case).

Env: MySQL 4.1, MySQL 5.0

Thanx
Phil