More than 5,000 police officers and troops will be deployed throughout Australia's biggest city, Sydney, for next month's Asia-Pacific Economic Cooperation (APEC) summit. It is the biggest security operation Australia has ever seen. From Sydney, Phil Mercer files this report.

Police navigate through a maze of water-filled barriers surrounding entrance of Convention Center at Darling Harbor, as preparations continue for next week's APEC summit, 31 Aug 2007

It is the biggest international conference the country has ever held. Twenty-one world leaders are expected to attend, including U.S. President George Bush, his Russian and Chinese counterparts and the Japanese Prime Minister.

APEC has turned parts of central Sydney into no-go areas. A protected zone fences off the Opera House, where many of the APEC meetings will take place, and some of the larger hotels where delegates will be staying.

A five-kilometer steel fence is being built to protect key sites from protesters and Australian police have cleared jail cells to make way for any mass arrests. Officers have been given new powers to stop and search citizens.

There will be strict counter-terrorism measures too.

Navy ships will guard Sydney harbor while in the skies overhead Blackhawk helicopters and fighter jets will be on patrol.

Aircraft will be barred from flying above the city and harbor ferries will be monitored.

The New South Wales Deputy Police Commissioner Andrew Scipione believes Sydney is well prepared to host such a high profile event.

"This is the biggest security event that's ever been hosted in the history of Australia, which is why we are going to the extraordinary lengths that we are. At a time when we are living in heightened times of terrorism and certainly there is significant protest activity around," said Scipione. "So yes, this is definitely the biggest event of its type ever hosted here in Australia."

Thousands of protesters are planning to voice their feelings during the APEC summit.

Various groups including students, trade unions and other left-wing activists are planning a series of demonstrations and rallies during the weeklong APEC meetings.

The largest protest is expected to draw thousands of people onto the streets on September the 8, the first day of talks among APEC's 21 leaders.

Organizers have insisted they want to make their point peacefully but the police are preparing for violence.

Many residents have complained about the road closures and the cost of security.

APEC promotes trade and economic coordination along the Pacific Rim.