Prime Minister Stephen Harper arrived in Australia Thursday, set to discuss climate change with the leaders of some of the biggest greenhouse gas emitters in the world.

Harper, who landed in Sydney in the afternoon after a 26-hour flight from Ottawa, will meet with 21 leaders at the Asia-Pacific Economic Co-operation conference at the famed Sydney Opera House.

Included in the talks which end Sunday will be the heads of energy-guzzling states like China, Russia and the United States.

Harper will begin his formal agenda Friday, delivering a speech on climate change and energy policy to business leaders. U.S. President George W. Bush will also be part of the event.

Bush and Chinese President Hu Jintao sat down one-on-one Thursday to discuss an array of contentious issues, including the political situation in Iran, the numerous recalls of China-made food and products, and the state of human rights in China.

"He's an easy man to talk to," Bush said after the 90-minute meeting. "I'm very comfortable in my discussions with President Hu."

Hu said the discussion was "candid and friendly," even though it touched on deep U.S.-Chinese differences.

"We both expressed a desire to work toward further development and growth of the business and commercial ties to our two countries," Hu said.

"We also talked about climate change," he added. "We believe that the issue of climate change bears on the welfare of the whole humanity and sustainable development of the whole world. And this issue should be … tackled through a stronger international co-operation."

The APEC meetings are expected to focus on key issues such as the stalled World Trade Organization negotiations, the formation of a Pacific-wide trade pact, energy and security.

Authorities in Sydney have implemented unprecedented security measures, including 5.5-kilometre steel-and-concrete fence to protect delegates from terrorist threats, as well as the thousands of demonstrators expected to descend upon the city.

Some 3,500 police and 1,500 counterterrorism and special forces have been deployed for the conference.

After the conference, Harper is scheduled to spend another two days in Australia on an official visit during which he'll be the first Canadian prime minister to address that country's Parliament.