Technically that is the suppliers responsibility. If you need it for 20/05 and it takes them 10 days to make and 3 days to ship then they have to start on 07/05 to make your required date. They then also “Confirm” this depending upon your process. As the purchaser I tell the supplier when I want it, it should calculate the delivery date from the lead time they have given you (it is up to them if they include transport time or not). As the purchaser you do not control this, or indeed how they ship and absorb the costs (unless you pay for specific delivery methods of course).
You so not schedule the suppliers resources, factory, raw material flow etc. They do.