UNITED NATIONS — Leonardo DiCaprio’s movie roles have made him an international star, but his long and little-known commitment to preserving the global environment has led to his new role — as a U.N. Messenger of Peace.

Secretary-General Ban Ki-moon announced on Tuesday that the 39-year-old American actor will join 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, primatologist Jane Goodall and conductor Daniel Barenboim.

Ban told a news conference that Dicaprio “is not just one of the world’s leading actors” but he has “a longstanding commitment to environmental causes.”

He said DiCaprio will focus his U.N. role on climate change issues.

“His global stardom is the perfect match for this global challenge,” the secretary-general told a news conference.

Ban said DiCaprio’s first act as a Messenger of Peace will be to address the climate summit he is holding next Tuesday on the sidelines of the U.N. General Assembly’s annual ministerial meeting, which 120 world leaders are expected to attend. Ban said the aim is to promote commitments to curb greenhouse gas emissions and pave the way for a global climate agreement in 2015.

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. According to the U.N., the foundation through grants, media projects and public campaigns and appearances by DiCaprio, has brought attention and funds to three areas — protecting biodiversity, conservation of oceans and forests, and climate change.

DiCaprio said in a statement that he is honored to be a Messenger of Peace and support the secretary-general “in his efforts to address one of the most important issues we face as a global community.”

“I feel a moral obligation to speak out at this key moment in human history — it is a moment for action,” he said. “How we respond to the climate crisis in the coming years will likely determine the fate of humanity and our planet.”

DiCaprio gained international fame for his role in “Titanic” and has been nominated for five Academy Awards, including for “Aviator” and “The Wolf of Wall Street.” He won Golden Globes for his performance in “Aviator” and “The Wolf of Wall Street.”