The White House says Obama discussed his plans Thursday in a phone call with German Chancellor Angela Merkel.
The summit is slated to be held during the September meeting of the U.N. General Assembly.
The White House says Obama praised Merkel's leadership on the Syrian refugee crisis and discussed plans to ask more countries to step up their contributions.
The leaders will raise the issue at a donors conference slated for February 4 in London.
Obama also expressed his condolences for the January terrorist attack in Istanbul. Ten Germans were killed when a suicide bomber set off the explosion near a group of tourists.