The countries using the euro currency will together provide aid worth between 20 billion and 25 billion euros ($27.2 billion and $34 billion ) for Greece, according to Germany's Finance Ministry, a magazine reported on Saturday.

Citing initial considerations by the ministry, German weekly Der Spiegel said the share of financial aid for Greece would be calculated according to the proportion of capital each country holds in the European Central Bank.

A spokesman for the German finance ministry said he would not comment on the report, which stated that the financial assistance should take the form of loans and guarantees.

The report said all euro countries would shoulder the burden and that Germany's share in the package would amount to four billion or five billion euros, and be handled by state-owned bank KfW.

According to the German planning, the aid should be tied to strict conditions, the magazine said, adding that loan tranches should only be paid out once these are met.

Chancellor Angela Merkel's government has so far resolutely deflected appeals to promise Greece aid despite fears that failure to help Athens could threaten the euro.

In public, Germany argues that leniency would take pressure off Athens and other euro zone debtors to cut their budget deficits. Behind the scenes, lawmakers acknowledge that Berlin has prepared measures if a rescue becomes inevitable.

A senior financial official in the ruling coalition told Reuters last week Germany was considering using the KfW to buy Greek government bonds. A separate proposal saw the KfW issuing guarantees to German banks that bought the Greek bonds.

Separately, Der Spiegel said that an internal report by Germany's financial market watchdog BaFin concluded that German banks could be seriously threatened if Greece or other countries including Spain, Portugal and Italy become insolvent.

(Reporting by Dave Graham and Holger Hansen; Editing by Angus MacSwan)