This would allow scientists to develop fast-growing trees with a maximized capability of storing carbon dioxide (CO2), one of the gases thought likely to be responsible for the heating of the earth's atmosphere.

Under the terms of the UN Kyoto Protocol on global warming, rich countries will be able to plant forests in the developing world and offset the amount of gas absorbed against their own greenhouse emissions.

The agreement in principle was scheduled to be sent to environment ministers at a meeting of the 180-nation UN Framework Convention on Climate Change here this week.

As part of the compromise draft agreement, countries in which it is proposed to plant genetically-modified forests must carry out detailed risk assessments and avoid the planting of what are known as invasive species -- those that drive out species native to the region.

An Italian spokesman, Aldo Iacomelli, said the agreement was worked out by the German and Brazilian co-presidents of the conference.

Environmental groups have been campaigning against such an extension of biotechnology. And scientists say that growing trees is only a temporary solution to the CO2 buildup.

The trees store the gas when they are growing, but give it all back when they die.

The Kyoto protocol was severely limited by the walkout in 2001 of the United States, the world's biggest polluter.

The agreement has to be ratified by Russia before going into effect, and delegates were hoping that an agreement on forest carbon sinks would persuade Russia to stop dragging its feet on Kyoto.

SPACE.WIRE