Obama warns against Asia 'intimidation'

US President Barack Obama yesterday warned of the dangers of outright conflict in Asia, as China squares off against rival claimants over disputed territories, but vowed that Washington would remain anchored in the region.

Obama said that Asia's security must not be based on intimidation of small nations by big ones. He insisted that security in the region must depend on mutual alliances.

In a speech at Brisbane's University of Queensland, ahead of the G20 summit, he also insisted that his "pivot" of US policy back to Asia was real and here to stay.

The two-day G20 summit will focus on promoting economic growth. World leaders are expected to expand on plans agreed by G20 finance ministers in February to boost global growth by 2% in five years.

UN Secretary General Ban Ki-moon also urged those attending to meet the challenges posed by Ebola, climate change and the conflict in Ukraine.

Meeting on the margins of the summit, Russian President Vladimir Putin urged his French counterpart Francois Hollande to join him to defuse tensions between the two countries over Ukraine.

France has withheld the delivery of two warships to the Russian navy over its actions in Ukraine.

The Russian president also discussed "rebuilding relations" with the UK after a bilateral meeting with Prime Minister David Cameron, Putin's spokesman Dmitry Peskov said.

Before the summit began, Cameron said Russia could face further sanctions unless it stopped "destabilising Ukraine".

But Putin faced a frosty reception from Canadian Prime Minister Stephen Harper over Russia's military assertiveness in Ukraine.

"I'll shake your hand, but I only have one thing to say to you: you need to get out of Ukraine," Harper told the Russian leader.

Earlier President Obama said Russia's "aggression" towards Ukraine was a "threat to the world".

President Obama did not mention China explicitly but he warned of the dangers posed by territorial disputes in the South China Sea, where Beijing's actions have raised concern among its neighbours.

He also said that all countries had to increase prosperity, warning that America could not "carry the global economy on its back".

Opening the summit, Australian Prime Minister Tony Abbott said he wanted to use the event to reassure people about the direction of the world's economy, with a "message of hope and optimism".

He said job creation, identifying tax cheats and strengthening the global economy would all be discussed.

His government had tried to keep climate change off the agenda, despite calls from campaigners.

However, Obama yesterday said a Sino-US 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.

More than 200 protesters buried their heads in the sands of Bondi Beach on Thursday in a demonstration over climate change inaction.

The Australian government is facing criticism over its climate policies. Since coming to power, Abbott has axed a carbon tax and overseen a 70% fall in investment in renewable energy.

In other developments, G20 leaders released a statement in which they vowed to do all they could to "extinguish" the Ebola outbreak in West Africa.

It said that members state were committed to do what was necessary "to ensure the international effort can extinguish the outbreak and address its medium-term economic and humanitarian costs".

The summit is taking place amid tight security, with some 6,000 police deployed. Twenty-seven different groups have been given permits to protest at designated areas.