UNITED NATIONS, Aug. 28 (Xinhua) -- UN Secretary-General Antonio Guterres reaffirmed the United Nations' principled position in support of a full, immediate and unconditional ceasefire as a first step toward a just, comprehensive and sustainable peace for Ukraine, in line with the UN Charter, international law and relevant UN resolutions, his spokesperson said Thursday.

The UN chief had a phone call with Ukrainian President Volodymyr Zelensky on Thursday, and the two discussed recent diplomatic efforts to end the war in Ukraine, Stephane Dujarric, the spokesperson, told a daily briefing.

The secretary-general stressed the importance of sustaining the diplomatic momentum, said the spokesperson.

The UN chief also reaffirmed the commitment of the United Nations to continue to address Ukraine's humanitarian needs on the ground and support recovery and reconstruction efforts, Dujarric added. ■