Australian Prime Minister Julia Gillard delivers a speech at the end of the G20 Summit of Heads of State and Government in Los Cabos, Baja California, Mexico

Playing her part ... Julia Gillard will confirm Australia's commitment to sustainable development, announcing the introduction of a national carbon tax to the United Nations conference. Photo: AFP

JULIA GILLARD will throw Australia's weight behind the push for new ''sustainable development goals'' which will set clear standards on nations' sustainable use of food, water and energy, when she addresses almost 100 world leaders at the Rio Conference .

The Prime Minister will also tell the United Nations conference in her address early today, Sydney time, that Australia is ''playing its part'' in moving to clean economic growth by introducing the carbon tax, which begins in just over a week.

Each leader makes one short official speech on the floor of the conference. But Ms Gillard has already conceded the outcomes of the global meeting will not ''make an indelible mark on world history''.

The document endorses sustainable development goals, but deep disagreement from some developing nations meant it could not include a timetable, nor even the specific themes they should cover.

''When we set targets we put before ourselves a task which is practical and empirical,'' she will say, describing any global collective action as ''exquisitely hard''.

The federal opposition has said the Rio conference will be a failure for Australia unless it reaches a global pact on carbon pricing, but it is not a meeting primarily focused on climate change and carbon pricing is not on the agenda.

Ms Gillard's schedule is focused on events organised on the sidelines of the meeting, which some observers argue are becoming more important for practical outcomes than the gruelling negotiation about sustainable development.

Yesterday she had breakfast at a function with Indonesia's President Bambang Yudhoyono and lunch with the Brazilian President, Dilma Rousseff, and other leaders.

On Wednesday, the UN Secretary-General, Ban Ki-moon, appointed her to co-chair a group of global leaders and celebrities making a ''final push'' for implementation of the millennium development goals by the target date of 2015. He said Ms Gillard's ''vision, leadership and commitment'' had caused him to choose her to lead the group, which includes the singer Bob Geldof, CNN founder Ted Turner, the UN special advisor Jeffrey Sachs and Graca Machel, formerly a minister in Mozambique and also the wife of the former South African President Nelson Mandela.

The goals include alleviating poverty, increasing access to clean water, food and education and for developed countries to meet targets on foreign aid spending, although Australia had to delay meeting the aid target for one year in this year's budget as part of its push to return to surplus.

Ms Gillard replaces the former Spanish Prime Minister Jose Luis Rodriguez Zapatero, who lost office last year, and her co-chair is the Rwandan President, Paul Kagame.

The leaders in Rio are expected to endorse a 49-page non-binding agreement on sustainable development and poverty eradication, already settled by their negotiators.

Environment groups said the document was watered down so much it was almost meaningless.