Feuding G20 leaders found common ground on Saturday in vowing to "extinguish" the Ebola outbreak as they worked to revamp the global economy at a summit marked by discord over Ukraine and climate change.

Along with the crisis between Ukraine and Russia, a surprise Sino-US pact on global warming has upset Australian Prime Minister Tony Abbott's desire to emerge from the Brisbane summit with a singular focus on reviving economic growth around the world.

Western leaders including Abbott were particularly incensed with Russian President Vladimir Putin over the downing of a Malaysia Airlines passenger jet over Ukraine in July.

At one point Saturday, Canadian Prime Minister Stephen Harper was approached by Putin in Brisbane to shake hands.

Harper said, according to Canadian media: "Well, I guess I'll shake your hand, but I only have one thing to say to you: you need to get out of Ukraine."

However, Putin appeared to use another bilateral meeting with French President Francois Hollande in Brisbane to try to defuse some of the tension, with the two governments at odds over a long-delayed deal to transfer two French warships to the Russian navy.

"We have to do everything we can to minimise the risks and the negative consequences for our bilateral relations," Putin told Hollande, before reporters were ushered out of the meeting.

In contrast, there was concordance at the G20 on the need to turn back an outbreak of Ebola that has so far claimed more than 5,000 lives across eight countries, particularly in west Africa.

"G20 members are committed to do what is necessary to ensure the international effort can extinguish the outbreak and address its medium-term economic and humanitarian costs," the leaders said.

However, there was no G20 cash commitment to back up the statement, despite appeals from aid groups, the World Bank and UN chief Ban Ki-moon for concrete actions that would allow Sierra Leone, Liberia and Guinea to fight the disease more effectively.

- 'Hope and optimism' -

Ban said the secondary impacts of the health crisis could include serious disruption to farming in the west African countries.

"That could provoke a major food crisis affecting one million people across the region," he said in Brisbane.

Ban also echoed former Soviet Union leader Mikhail Gorbachev's fears that tensions between Russia and the West had brought the world to the brink of a new Cold War, and described climate change as "the defining issue of our times".

But Abbott -- who is sceptical about man-made climate change -- has fought hard against mentioning global warming in the G20's closing statement and was said by delegates to be haggling with the US and Europeans over the final wording.

However, campaigners said events this week had left Abbott isolated on the issue and unable to thwart a redoubled international drive to craft a new global agreement in Paris next year.

US President Barack Obama said the breakthrough in Beijing this week on reducing carbon emissions proves that a post-Kyoto deal to arrest climate change is achievable, as he unveiled a $3 billion pledge to a UN-backed climate mitigation fund.

"If China and the US can agree on this, then the world can agree on this -- we can get this done," he said in a speech in Brisbane.

Obama also said the United States cannot "carry the world economy on our back", urging G20 leaders to work harder to create jobs by revving up growth in the aftermath of the worst financial crisis since the 1930s.

Addressing the G20 conclave, Abbott ticked off a list of geopolitical challenges ranging from instability in eastern Europe and the Middle East to Ebola in west Africa and fragile economic growth.

"This is the world's work that we are engaged on," he said, reminding the G20 leaders that together their countries amount to 85 percent of the planet's gross domestic product and 65 percent of its population.

"But the message that should come from us over these next two days is a message of hope and optimism. Yes, our world can grow and, yes, our world can deliver the jobs that our people want," Abbott said.

A draft copy of the "Brisbane Action Plan" to be adopted Sunday said that, owing to worries about sluggish conditions worldwide, the leaders will agree to reforms that could accelerate growth by 2.1 percent, up from a previous target of 2.0 percent.

That, according to Abbott, will translate into more than two trillion dollars in extra growth and millions of new jobs.