Germany's foreign minister is calling for U.N.-supervised humanitarian access to the contested Syrian city of Aleppo and says a unilateral three-hour daily cease-fire isn't enough.

The Russian military, which is fighting alongside Syrian government forces in the civil war, has promised a daily, three-hour cease-fire for Aleppo to allow humanitarian aid into besieged areas. A senior U.N. humanitarian official already has said that a 48-hour pause each week is needed in view of the logistics of providing aid.

German Foreign Minister Frank-Walter Steinmeier was quoted as telling Friday's edition of the daily Frankfurter Allgemeine Zeitung that "humanitarian access can't be under the single-handed control of one side of the conflict."

He added that "a unilaterally declared three-hour cease-fire per day isn't enough to avoid a humanitarian catastrophe."