In a new report, the Washington-based organization also called for "forceful" reductions in greenhouse gases to forestall some of the worst consequences of climate change.

The bank urged countries in the region to dramatically increase their efforts to prevent climate change and mitigate its negative impacts, including drought, diminishing agricultural yields, vanishing glaciers and raging floods.

"Many climate-related changes are irreversible and will continue to impact the region over the long term," Walter Vergara, the bank's Division Chief of Climate Change and Sustainability and the lead researcher of the study, said in a statement.

"To prevent further damages, adaptation is necessary but not enough. Bolder actions are needed to bend the emissions curve in the coming decades," he said.

The report -- issued by the bank, the Economic Commission of Latin America and the Caribbean (ECLAC) and the World Wildlife Fund (WWF) -- is to be formally unveiled later this month at the Rio+20 United Nations Conference on Sustainable Development.

The gathering in Rio de Janeiro of more than 100 heads of state and tens of thousands of participants from governments, the private sector and NGOs will mark the 20th anniversary of the 1992 "Earth Summit" in the Brazilian city.

More than 100 heads of state and government are expected to attend the Rio de Janeiro summit on June 20-22, but months of talks have failed to produce an agenda for the event which is to mark the 20th anniversary of the Rio Earth Summit.

"We need world leaders to make the issues on the table at Rio+20 their own personal priority. Nothing else will do," Ban told reporters at the UN headquarters.

Ban is battling to rescue the summit, which he warned this week must guide the world away from a "tragic" end.

The UN Conference on Sustainable Development is taking on the vast challenge of transforming environmental, social and economic policy to cope with a world population racing past seven billion, exhausting dwindling resources and straining cities to the limit.

Ban and specialist groups have however accused governments of putting national interests before the common good in months of agonizing negotiations before the Rio summit.

Another three days of talks on the agenda will be held in Rio from June 13. Some diplomats say the Brazilian hosts are expected to step in to produce a tlimeline agenda from the 80 page document that the UN's 193 members are currently haggling over.

"I am cautiously optimistic," said Ban. "I am sure that member states will act for the interests of humanity. This is a once in a generation opportunity. Once they miss this opportunity they may have to wait a very long time."

The summit has to agree on steps to boost the so-called green economy, set out Sustainable Development Goals on areas ranging from global health and poverty to preserving oceans and natural resources, and decide how new targets should be policed.