A polite way of telling someone you have to let them go

What is a polite way of telling a long-term and loyal employee that you have to let them go? I know the word απολύω, but I'm wondering if there is something a little softer. This is a very difficult task I have to face and I want to find the nicest way of doing it possible.

The full sentence would be: "Due to circumstances beyond my control, I am, unfortunately, going to have to let you go."

Thank you.

«Εξαιτίας περιστάσεων πέρα από τον έλεγχό μου, δυστυχώς, προς μεγάλη λύπη μου, πρέπει να διακόψουμε τη συνεργασία μας...»

Thank you very much. This is very helpful.