Transaction Abort during insert using libpq

Hi all,
Can anyone tell me if there is a way to avoid Postgres automatically
aborting a transaction under certain error conditions.  In particular,
if I try to insert a record into a table and the insert fails due to a
duplicate key on a unique index my whole transaction is aborted.
I would prefer to get an error rtn that indicates reason for failure
but lets the rest of the transaction continue normally unless I choose
to roll it back.  I am using PostgreSQL 7.0 with libpq.

Thanks
Kevin English