But despite promises at a summit in 1992 that industrial states should provide development aid of 0.7 percent of their gross domestic product, aid flowing to poor countries has dropped both in relative and in absolute terms, Toepfer said.

"We cannot dare again disappoint people, so we must be honest. We cannot give promises we really cannot deliver," he told Reuters in an interview.

Toepfer was speaking during a two-day meeting of scientists, diplomats and environmentalists in Stockholm to mark 30 years since 114 nations, excluding the former Soviet bloc, agreed on a common duty to protect the global environment.

Fighting poverty - with the aim of halving the number of people living in poverty by 2015 - and reducing environmental damage will also be the main topics when world leaders and non-governmental organisations meet at a huge U.N. summit in Johannesburg at the end of August.

"Johannesburg must not be a summit of new declarations and new programmes, it must really be a summit on implementation of concrete action," Toepfer said.

Global accords on biodiversity and greenhouse gas emissions should now be put into force and actual results are needed more than new rounds of speeches, he said.

OPTIMISTIC ABOUT U.S. PARTICIPATION

But since a final preparatory meeting in Bali ahead of the Johannesburg "Earth Summit" ended without agreement, conservationists have said the meeting's draft text is all talk and no action and the meeting is shaping up to be a major flop.

Environmental action group Greenpeace has accused the United States and other countries of systematically removing anything smacking of action from the draft text.

It is also still unclear whether U.S. President George W. Bush, who last year rejected the Kyoto Protocol on global warming, would attend the 10-day summit with more than 100 heads of state.

But Toepfer said he was optimistic Bush would participate.

"I am still convinced that the United States too will be aware of the need for their leadership. I am also realistically optimistic that the United States will play their part and the decision (whether Bush will attend) will be very carefully considered,"he said.

The U.S. focus on a war against terrorism launched after the September 11 attacks last year should not prevent it from trying to promote environment conservation and reduce poverty in developing countries, he said.

"More than ever we have to fight all together against terrorism, but we must also use this alliance against hunger and hopelessness, and for globalisation with a human face," he said.