The ceremony appointing the 2004 Nobel Peace Prize winner to the prestigious position as a peace envoy will take place from Tuesday afternoon at the climate change conference in Copenhagen, he said.

"Professor Maathai's long record of achievement in environmental conservation and sustainable development makes her an excellent choice," Ban told reporters before flying to Copenhagen.

Maathai, the first African woman to win the Nobel Peace Prize, was cited for her work in conservation, women's rights and clean government. She founded the Green Belt Movement, which led to the planting of 30 million trees throughout Kenya.

Maathai will become the 12th UN Messenger of Peace, joining a list of notable figures including fellow Nobel laureate Elie Wiesel, actors George Clooney and Michael Douglas, pop star Stevie Wonder, primate expert Jane Goodall and conductor Daniel Barenboim.

"But we also see tangible progress on core issues of technology cooperation and financing. We have reached substantial agreement on fast track funding for mitigation and adaptation," he said.

"Looking ahead, we need greater clarity on a robust finance package for the middle and longer-term. It is essential that we leave Copenhagen with a clear

understanding of how we will meet the financing challenge through 2020," he added.

"We must also recognise that Copenhagen is only a beginning. Ultimately, success will be measured by our progress on the ground. That is why, in Copenhagen, I will attend to some practical matters of implementing an agreement," said the Secretary General.