Earlier, Kevin Rudd, Australia's prime minister, handed formal papers to Ban regarding his country's observance of the Kyoto Protocol.
Rudd said Australia was already suffering from climate change, ranging from a drying up of rivers to disruptions to corals of the Great Barrier Reef.
He said: "What we see today is a portent of things to come."
Australia's decision isolates the US as the only rich nation without binding caps on greenhouse gas emissions under the UN deal which stretches to 2012.
Ministers at the conference are split over the ground rules for starting formal negotiations on a new long-term global treaty to limit greenhouse gas emissions.
Plea to act
Ban said: "Not only are the eyes of the world upon us. More important, succeeding generations depend on us. We cannot rob our children of their future."
Ban said that the Bali meeting should agree to a firm two-year deadline to agree a successor to Kyoto that would involve action by all nations, including the US and poor countries led by China and India, whose emissions are soaring.
He said: "You need to set an agenda, a roadmap to a more secure climate future, coupled with a tight timeline that produces a deal by 2009."
The UN wants a new pact adopted at a meeting in Copenhagen in late 2009.
Some developing nations, worried that any commitments to curb fossil fuel use might slow economic growth, want Bali to launch only non-binding talks.
The US opposes many other nations' hopes for the guiding terms for negotiations, which include a non-binding range for rich countries to cut greenhouse gases by 25-40 percent below 1990 levels by 2020.
Susilo Bambang Yudhoyono, Indonesia's president, won applause from delegates by saying the US should be part of any new deal, as the world's biggest economy and top greenhouse gas emitter.
He said: "We are embarking on the biggest project in human civilisation. We must ensure that the United States ... is part of such post-2012 arrangements."