Hundreds of people have been killed in a concerted push by the government and its allies to quash resistance in the rebel-held eastern part of Aleppo and re-establish control over what was once Syria's biggest city.
"The ICRC is trying hard to engage with all parties to this conflict to find a solution to have access to all those people," Maurer told a press conference in Dublin on November 21. "We haven't seen any humanitarian assistance in a month. This is a question of urgency."
Maurer said he would meet Russian Prime Minister Dmitry Medvedev on November 24, then fly on to Washington and Tehran.
"We are ready to deploy within record time if we have access," Maurer said.
"If we do not bring food, medicines and baby food to occupied Syrian cities, then those goods will not be available, especially to the most vulnerable people. There is no Plan B."