The Armenian midfielder is highly rated and sought after following a superb season last time around for Shakhtar Donetsk.
Palkin told Futbol: “I don’t know where Mkhitaryan is now, solely his agent knows this.
“Borussia offered €23m (£19.5m) for the midfielder. I contacted Mkhitaryan’s agent yesterday. I wrote to him about the official position of the club.
“We are prepared to sell Mkhitaryan for €30m (£25m), this offer stands for the next 10 days. If Mkhitaryan wishes to leave, they have to pay this amount for him.
“€30m, one installment. If there is a club that can pay that amount, we are ready to make a deal.”
