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."

DeCaprio 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.

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The secretary-general said DiCaprio will address next Tuesday's climate summit where he expects some 120 world leaders.

DiCaprio, 39, 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.

Last year, DiCaprio starred in the films "The Wolf of Wall Street" and "The Great Gatsby." He'll next be seen in "The Revenant" with Tom Hardy, due out next year.