Prince Charles arrived in Brazil Wednesday with a warning that time was running out for the world to come up with a coordinated plan to combat climate change.
The heir to Britain's throne was expected to make a passionate plea in Rio de Janeiro on Thursday for action.
We have only "100 months left" to save the planet from irreversible damage, he is to argue, according to excerpts given in advance to British media.
The prince, accompanied by his wife Camilla, was to follow up the speech with a trip to Brazil's vast Amazon jungle, to see first-hand the effects of man's impact on nature.
He was then to wrap up a 10-day tour to Latin America with a trip early next week to the Galapagos Islands -- the nature reserve archipelago off Ecuador whose abundant wildlife inspired Charles Darwin to draft his theory of evolution.
Prince Charles gave a preview of his environmental campaigning on the first leg of the three-nation tour, in Chile.
"I must insist that if we want to leave our children a better world, we must act together, and we must act now," he said at a dinner hosted by Chilean President Michelle Bachelet in his honor late Monday.
He is backed by the British government which has described countering climate change as one of its highest priorities this year.
During his Chilean stay, the prince, 60, and his wife, 61, got close to excited crowds, shaking hands with dozens of people who had turned out to see them Tuesday in the port of Valparaiso.
"It was moving, all very emotional. I touched both their hands," said one woman.
The royal couple visited a Chilean naval base in the port, as well as a former British frigate that is now being used by Chile.
They also inspected an organic wine property nearby and a biofuel company before returning to the capital Santiago.
Following their arrival in Brasilia on Wednesday, they were to meet Brazilian President Luiz Inacio Lula da Silva.
On Thursday, Prince Charles and Camilla were to go to Rio for the speech, billed as the most important part of the tour. Their Amazon trip was to take in the northern towns of Manaus and Santarem.
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