temporarily offset foreign key constraints

["George Kao" <george(dot)kao(at)group-upc(dot)com>]

Hello, 
 
Is there any sql command that is equivalent to 
set foreign_key_checks=0;  (of Mysql)
in posgresql?
 
Basically, I would like to some updates of data on the key field which has
the foreign key constraints? Any suggestion of how this can be achieved?
 
Thanks
George