Russia lifts ban on delivery of S-300 missiles to Iran

[arjunadawn]

Where is the threat to Israel now, do these missiles pose a threat or is it just that Iran having this missile system would make it more difficult for Israel or anyone else to attack Iran ?

They are a deterrent. They are not offensive weapons. But deterrents cannot be considered solely in this manner. When deterrents significantly shift the balance of power with regard to others they can be considered a threat. (Example: US European missile shield and Russian responses).