Existing users with same username as ldap fails to import

I am trying to solve a problem i am stuck at.
I have incremental users in hr application i am planning to import as soon as the user gets added and allow him to login using created password on temporary basis but this user will get added to ldap i.e AD after 10 days or a month depending on onboarding.But in this case i will be required to manually delete the user and he will get automatically federated. I want to avoid this as soon as the user is added to ldap he must be able to login using ad password.
Is there any way to achieve this??