Secretary-General Ban Ki-moon has appointed Leonardo DiCaprio as a United Nations Messenger of Peace to help promote global action on climate change.
Ban told a news conference Tuesday that the American actor "is not just one of the world's leading actors" but he has "a longstanding commitment to environmental causes."
DiCaprio established a foundation in 1998 with a mission to promote the Earth's last wild places and build a more harmonious relationship between humanity and the natural world.
The secretary-general said DiCaprio will address next Tuesday's climate summit, where he expects some 120 world leaders.
DiCaprio said he was honoured by the role and that he feels "a moral obligation to speak out at this key moment in human history" about the threat of climate change.
The 39-year-old "Wolf of Wall Street" star founded an environmental foundation in 1998.
He joins 11 other prominent world figures who advocate on behalf of the U.N. as Messengers of Peace, including Stevie Wonder, Michael Douglas, George Clooney, Brazilian author Paulo Coelho and conductor Daniel Barenboim.
