Can i force deletion of dependent rows?

Hello,

I have 2 tables (A and B) where the table B has a foreign key reference to table A.   Like this:

create table A (x int primary key);
create table B (y int primary key, z int references A (x) );

As you can see, i've not specified any further 'on delete' clause to the foreign key constraint like 'on delete cascade' or 'on delete restrict' or 'on delete set null' or 'on delete set default'.   This means that the default behavior is followed ie 'on delete restrict' holds by default.

Now I want to delete a particular row from table A.  Is there any way I can force deletion of all the dependent rows in table B? 

Note that the tables have already been created in the above manner and populated.  I want to do this deletion through DML only ie without any change in the table definition.

Thanks,
Shruthi