There have been more moments of regret than pride in accomplishments in 10 years at the United Nations, Secretary-General Ban Ki-moon said Friday as he prepares to leave office at the end of the year.

The carnage in Syria, the risk of genocide in South Sudan and maintaining momentum on the Paris climate change accord all weighed on his mind, the world's top diplomat said at his last press conference at UN headquarters in New York.

Syria has left a "gaping hole in the global conscience" and "Aleppo is now a synonym for hell," Ban said, while the deteriorating situation in South Sudan now threatened to turn into genocide. There is no turning back on the Paris climate change agreement and it must be supported in order to save humanity and the environment, Ban said, likely referring to US president-elect Donald Trump's position against acting on climate change.

'Fires still burning'

From violence in Mali to Yemen and the Central African Republic, the "fires are still burning" in conflicts that seemingly know no end due to narrow political and personal interests and a lack of global solidarity, Ban told reporters.

"This has been a decade of unceasing test," Ban said, reflecting on his 10 years at the UN. "But I have also seen collective action change millions of lives for the better."

"Difficult as it may sometimes be, international cooperation remains the path to a more peaceful and prosperous world," Ban said.

South Korean politics

Ban also addressed speculation he plans to run for president in South Korea, where President Park Geun-hye was impeached in a massive corruption scandal that has shaken the nation.

"I'll go back to Korea, then I'll try to meet as many people as possible, which may include political leaders, leaders of civil society and my friends, and I will really consider seriously how best and what I should and could do for my country," Ban said.