change Country/Region when store credit in balance

I originally I registed an iTunes account in USA many years ago, but today I live in Iceland.

in order to change Country/Region I received the error message "You have a store credit balance; you must spend your balance before you can change stores.". But there is no way to spend the exact amount and my european creditcards are not eligible for the US I-Tunes account.

("Your payment method is not valid in this Store. Please enter a new payment method.")

How can I change Country/Region (in order to make my credit cards eligible) when I still have store credit balance?

Please help me solve this issue ASAP as I urgently need to upgrade my ICloud account