More than two thirds of cuts in greenhouse gas emissions needed by 2030 to fight climate change will have to come from developing countries, the United Nation's climate change secretariat said on Thursday.

The world will need to spend hundreds of billions of dollars annually by 2030 to fight climate change and its effects, said the report on the "potential investment and financial flows" needed to avoid dangerous climate change.

The sum will equal about half a percent of global wealth.

"It's not just a question of throwing more money at the problem, it's also a question of putting in place smart policies," the U.N.'s climate change chief, Yvo de Boer, told Reuters.

Earlier this year, a panel of climate scientists and economists issued a report saying greenhouse gas emissions would have to peak by 2015 to keep the world on a course which the European Union says would avoid dangerous climate change.

The report issued on Thursday said emissions will have to drop in the ensuing 15 years to 2004 levels to achieve that.

The report split the fight against global warming into two parts: first, cutting mankind's contribution to the problem by curbing greenhouse gas emissions, and second, preparing for climate change that was now unavoidable.

The cost of returning greenhouse gas emissions to present levels by 2030 would be about $210 billion annually by then, through measures such as investing in energy efficiency and low-carbon renewable energy, the report said.

"To meet the main part of this goal of returning emissions to 2004 (levels) by 2030, you don't mainly need extra money but a shift in investments away from building new power generating capacity towards improving energy efficiency," said de Boer.

Some 68 percent of emissions cuts must take place in developing countries, the report said.

The other half of the problem, adapting to climate change, was more difficult to estimate, but would run into several tens of billions of dollars annually by 2030, the report said.