Update table equalize where same id but different country

I have a problem creating an SQL statement that would run in a cronjob every few minutes.

I want to equalize one column where ItemCodes (IDs) are the same but each country is different

Table:

+----------+--------+---------+

| ItemCode | OnHand | country |

+----------+--------+---------+

| 08040    | 450    | de      |

+----------+--------+---------+

| 08040    | 000    | hu      |

+----------+--------+---------+

| 08040    | 145    | si      |

+----------+--------+---------+

I want to take OnHand where country = de and put it in OnHand where country = hu. (for multiple ItemCode - have 7000 of them)

UPDATE sap_items
    ON sap_items.ItemCode = sap_items.ItemCode AND
       sap_items.country='de'
SET sap_items.OnHand = sap_items.OnHand
WHERE sap_items.country='hu'";

I understand that this is wrong. But i'm not sure how to properly put it.