delete with index scan

I have a table t1 with a primary key column pkey, and a table t2, with a primary key column pkey. Is there a way to make the following delete use the indexes?

delete from t1 where pkey in (select pkey from t2);

NOTICE: QUERY PLAN:

Seq Scan on t1 (cost=0.00..6616238.99 rows=660239 width=6)
SubPlan
-> Seq Scan on t2 (cost=0.00..20.00 rows=1000 width=8)

EXPLAIN

thanks,
Sally

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Sally Ruggero
Software Development

North Electric Company, Inc.
6131 Falls of Neuse Road, Suite 205
Raleigh, NC 27609

Office: (919) 341-6009
Fax: (919) 341-6010

Email: sally(dot)ruggero(at)northelectriccompany(dot)com