United Nations Secretary-General Ban Ki-moon appeared on Deutsche Welle's Conflict Zone program on Monday to talk about the dire humanitarian situation in Aleppo, Syria. In his interview, the South Korean statesman had some choice words for Syrian President Bashar al-Assad.

"It's true that because of his failure of leadership so many people have died, more than 300,000 have been killed," he told DW journalist Michel Friedman when asked if he considered the president a mass murderer.

In the course of the interview, Ban admitted that the United Nations ought to do more to prevent the kind of suffering the citizens of Aleppo are now experiencing on a daily basis: "Of course we should have started much earlier; we should have prevented Srebrenica, we should have prevented the Rwandan genocide. In Aleppo, we're making our utmost efforts. The future of one person, like President Assad, should not block this process."

The diplomat appeared to be referring to how the future role of Assad in Syria has been a consistent stumbling block between would-be peacebrokers, the US, who seek his ouster, and Russia, who have long supported him.

Ban: Not for me to say who is right

He declined, however, to criticize Russia for restarting airstrikes during a temporary truce, saying "as a secretary-general, I'm not here to make any determinations on who is wrong or who is right."

The UN leader also said that "the United States and Russia are working very hard" to minimize the plight of Syrians.

Ban also spoke on the future of the UN Security Council, of which the US and Russia are permanent members, saying that it ought to be "more democratic, more transparent, more representative…But unfortunately, member states have not been able to agree on anything including the size or formation of how this is possible."

UN secretary-general since 2007, Ban is set to step down next year. He will be replaced by Antonio Guterres, a former prime minister of Portugal and UN High Commissioner for Refugees. Ban's interview with Conflict Zone will air on Wednesday at 17:30 UTC.