UN chief Ban Ki-moon voiced hope Tuesday that US president-elect Donald Trump will understand the urgency of climate change and will "vary" threats to withdraw the US from the Paris climate-rescue pact.

"I have explained at length about our expectations and our hope that... president-elect Mr Trump will hear and understand the seriousness and urgency of addressing climate change," Ban told reporters in Marrakesh, before he was due to address a UN climate huddle. 

"As the president of the US, I am sure he will understand this, he will listen, he will vary his campaign remarks."