BRISBANE, Australia -- Stephen Harper and other G20 leaders began their annual summit in a tense atmosphere dominated by Western anger towards Russian President Vladimir Putin and pressure to address climate change, fight Ebola and kickstart economic growth.

A senior government source said the prime minister has no intention of talking at all to Putin during the summit, saying the Russian leader is well aware of Canada's position on his aggression in Ukraine.

The brilliant blue skies overhead this seaside city buzzed with security helicopters as the leaders, including U.S. President Barack Obama, arrived at the Queensland Parliament House in downtown Brisbane for a leaders' retreat.

Harper chatted with British Prime Minister David Cameron as they entered the stately stone building on a steamy morning. The city is currently enduring a record-breaking heatwave, with the mercury expected to climb as high as 40 C later in the day.

The prime minister arrived in sweltering Australia from chilly New Zealand late Friday night -- early Friday morning back in much of Canada --and told the media he agreed with Australian Prime Minister Tony Abbott, the summit's chairman, that the event should focus on economic issues.

Abbott wants his fellow G20 leaders to commit to pumping up economic growth by up to two trillion dollars in the years to come.

"I certainly respect the decision of Prime Minister Abbott to try to focus the G20 agenda on the purpose of the G20, which is the economy," Harper told a news conference in Auckland before heading to Brisbane.

But he added he expected the recent climate change deal between the U.S. and China, setting limits on greenhouse gas emissions, would also be a topic of discussion among the leaders of the world's top economies, as well as a host of other issues.

The United States is expected to announce later in the day that it's contributing US$3 billion to the so-called Green Climate Fund to help poor countries adapt to climate change and develop cleaner sources of energy.

The move reportedly is part of Obama's intention to use his last two years in office pushing forward climate change policy.

Environmentalists have demanded climate be on the agenda at the G20 meeting, and the head of the United Nations, Ban Ki-moon, called on the G20 to make the environment a priority in a news conference at the summit.

"Climate change is the defining issue of our times; it's only natural that G20 leaders should focus much more on this," he said.

Hundreds of protesters were in Brisbane staging largely peaceful demonstrations and marches, mostly to demand action on climate change from the leaders of the world's top 20 economies.

But there were protesters calling for action on a variety of issues under heavy police watch, including 100 Tibetan ex-political prisoners and supporters who urged world leaders to support an end to China's occupation of the region.

Violent protests have marred previous G20s, including in Toronto four years ago.

There was little doubt Putin's actions over the past few days, however, were top of mind for the leaders, with Abbott lashing out at the Russian leader for apparently flexing his military muscles by sending four Russian navy ships to stalk Australia's northern coast in the days leading up to the G20 summit.

Putin too arrived in Brisbane late Friday night as a number of Western leaders fumed at his actions, setting the stage for face-to-face meetings with his G20 colleagues that are certain to be crackling.

"Russia would be so much more attractive if it was aspiring to be a superpower for peace and freedom and prosperity, if it was trying to be a superpower for ideas and for values, instead of trying to recreate the lost glories of tsarism or the old Soviet Union," Abbott said.

Cameron threatened Russia with further sanctions if it doesn't resolve the Ukrainian conflict amid reports that Russian troops and tanks are flooding into the eastern reaches of Ukraine.

Harper has been a vehement Putin critic for months, with Canada and Russia trading a number of retaliatory sanctions.

Russia, meantime, took aim at France on the eve of the summit, threatening "serious" consequences if it fails to deliver a warship whose handover has been delayed by the events in Ukraine.

Putin also assailed his fellow G20 nations for imposing sanctions at all, saying in an interview with Russia's state media that the measures violated G20 principles.

The G20 is also facing calls to come up with a financial response to the Ebola epidemic in western Africa. Health-care workers battling the outbreak have been pleading for more resources.

World Bank president Jim Yong Kim says a proposed global emergency fund to contain the next Ebola outbreak has the interest of many finance ministers and central bank governors. He's in Brisbane for the summit.

A spokesman for Harper said the fund was an "interesting idea in principle."

"But we would need to see additional details on the mechanism, how it would work, and what the accountability measures would be," said Jason MacDonald.