LONDON - World energy consumption will rise rapidly over the next 20 years, pushing up costs and increasing greenhouse gases, unless a deal is reached to curb carbon dioxide emissions, the International Energy Agency (IEA) said Tuesday.

In its annual World Energy Outlook, the IEA said global energy demand would increase by an average of 2.5 percent per year over the next five years if governments made no changes to their existing policies and measures.

Under these circumstances, which the IEA called its reference scenario, world primary energy demand would rise by an average of 1.5 percent per year over the next two decades.

Oil demand, excluding biofuels, would increase by 1 percent per year to 105 million barrels per day (bpd) by 2030 from 85 million bpd in 2008.

The IEA argues strongly for a global deal at the United Nations Climate Change Conference in Copenhagen in December to limit greenhouse gases and spells out how sharply use of fossil fuels will increase if policies remain unchanged.

Fossil fuels remain the dominant sources of primary energy worldwide in the reference scenario, accounting for more than three-quarters of the overall increase in energy use between 2007 and 2030, the IEA said.

Natural gas demand would increase 1.5 percent per year to 4.3 trillion cubic meters (tcm) in 2030, under this scenario.

The main driver of demand for coal and gas would be inexorable growth in energy needs for power generation, it said, forecasting in its reference scenario that world electricity demand would grow by 2.5 percent per year to 2030.

The developing world will see some of the fastest rates of growth with the 10 countries of the Association of Southeast Asian Nations (ASEAN) seeing an average annual increase of 2.5 percent in their primary energy demand until 2030.

(Reporting by Christopher Johnson and Barbara Lewis; editing by William Hardy)