Is it permissible to pay a portion of the obligatory Zakat on money saved in the bank for the purpose of buying an apartment, knowing that paying the full Zakat might prevent the purchase of the apartment?

Zakat is obligatory on money saved to buy a house if it reaches the nisab (minimum threshold) by itself, or by combining it with other funds or trade goods, and a full lunar year (hawl) has passed over it. The fact that the money is not invested does not prevent Zakat from being due, because it is lawful, owned, and growing wealth. Whatever is disbursed with the intention of Zakat is deducted, and the remainder is also to be given out. It is not permissible to place money in an interest-bearing bank except out of necessity.