UEFA says Panathinaikos faces a one-season ban from European competition if it fails to pay creditors this month.
The Greek club had a 100,000-euro fine imposed by UEFA's club finance panel.
UEFA says a further 100,000 euros are due if Panathinaikos has not "paid the amounts or concluded an agreement with the creditors" by March 1.
UEFA did not specify the debts, though can intervene if clubs delay paying wages, transfer fees or taxes.
If Panathinaikos misses the deadline, it will be excluded from the next Champions League or Europa League for which it qualifies until 2021.
The 1971 European Cup finalist is eighth in the 16-team Greek Super League.