UN Secretary-General Antonio Guterres promised on Saturday to provide more humanitarian assistance to the Ukrainian people during a phone call with Ukrainian President Volodymyr Zelensky.

"The secretary-general conveyed to the president the determination of the United Nations to enhance humanitarian assistance to the people of Ukraine," according to a readout about the secretary-general's call with Zelensky.

The UN chief informed Zelensky that the world body "would launch on Tuesday an appeal to fund UN's humanitarian operations in Ukraine."

In an email, Stephane Dujarric, spokesman for the secretary-general, told reporters that because of the escalating situation in Ukraine, Guterres will not travel to Geneva as planned. Instead, "he will send a video message to Monday's meeting of the Human Rights Council," he added.