Oracle - adding foreign constraint in disabled state?

I need to add a foreign key constraint but initially it should be disabled. I can add it in create table sentence or in an alter table sentence, it does not matter. I do not know the reason behind this request (it may be ORA-02298: cannot validate (BLA.BLA_FK) - parent keys not found ) but I was asked to do it this way. So what is the correct sentence for this in Oracle database?