Aim to grow economy by $2t

Leaders from the world's richest nations will thrash out plans to grow the global economy by $2 trillion, generate jobs for millions and tackle corruption head-on at the biggest diplomatic gathering in Australian history starting today in Brisbane.

The G20 summit, costing taxpayers at least $400 million and commanding the lockdown of the nation's third biggest city, has as its target to agree on more than 1000 proposals that will boost world growth over the next four years 2 per cent more than has been forecast.

The summit is already in danger of being overshadowed by a speech today from US President Barack Obama, who will be flown into Brisbane to give an address on America's ties to Asia.

And an issue that Prime Minister Tony Abbott had sought to keep off the agenda - climate change - has been brought to the fore by Mr Obama, with his deal this week with China to slash greenhouse gas emissions and Washington announcing yesterday that Mr Obama will pledge $3.2 billion to a United Nations fund to help the poorest countries mitigate the effects of climate change.

Mr Obama is likely to touch on his deal with China in his speech to University of Queensland students today.

More than 7000 delegates, security and media are in Brisbane for the two days of talks that include Mr Obama, Chinese President Xi Jinping, British Prime Minister David Cameron, Indian Prime Minister Narendra Modi, Russian President Vladimir Putin and German Chancellor Angela Merkel.

Australia is seeking a two-page communique tomorrow afternoon, with all nations signing up to pledges that will boost economic growth through more spending on infrastructure, freer trade between nations and an overhaul of global tax and corruption laws. The centrepiece will be the 1000-plus proposals from all countries, though there are doubts they can all happen.

Australia's proposals include a series of Budget measures that the Government is struggling to get through Parliament.

Mr Abbott described the G20 as the world's premier economic forum, with countries at the meeting responsible for 85 per cent of global GDP and three-quarters of world trade.

"We've got a very strong mission in Brisbane to work for growth and jobs - growth and jobs. That's our focus," he said.