The chairman of the Joint Chiefs of Staff flew out of Yokota Air Base in Tokyo's western suburbs, US military media coordinator Masao Abe said.

"I cannot confirm where the plane is headed," he said. The US Embassy and US forces public relations offices here have refused to give details of Myers' itinerary.

In Washington, a US defence official said Monday that Myers was to visit China, Mongolia and Australia after Japan during a nine-day Asia-Pacific swing. But he did not give details out of security concerns.

Myers told a group of reporters in Tokyo on Monday that he would not rule out the possibility that Japanese troops would be the target of attacks during their deployment in Iraq to help humanitarian and reconstruction work there.

"Operations in Iraq are not without risk and it doesn't matter really where you are in the country. There are going to be challenges," Myers said, according to the Kyodo news agency.

He also said, compared with central Iraq, the security situation in northern and southern parts are "more stable" and have "less conflict."

The southern Iraqi city of Samawah, where Japanese troops are expected to be deployed, is perceived as being relatively safer than elsewhere in Iraq, where attacks and bombings against US personnel and Iraqis continue.

But given the methods of attacks by supporters of deposed Iraqi President Saddam Hussein and foreign Islamic extremists against the United Nations and coalition forces, he said, "You can never say that you are free from risk."

Myers is making the highest level US military visit to China since a US surveillance plane and a Chinese fighter collided in mid-air nearly three years ago, the official said.

North Korea and Taiwan were expected to come up in talks between Myers and military counterparts in Beijing, officials said.

Myers' visit to China is the next step in a gradual opening of military relations between the two powers, whose relations hit a low point on April 1, 2001 after a Chinese fighter crashed into a US Navy EP-3 surveillance plane over the South China Sea.

The pilot of the Chinese aircraft was killed and the crippled EP-3 was forced to make an emergency landing at a airbase on China's Hainan island, where the plane's crew was held for 11 days.

China's Defense Minister Cao Gangchuan met in late October with US Defense Secretary Donald Rumsfeld in an effort to normalize relations between their two militaries.

WAR.WIRE