The US's top military officer has said a military solution to the North Korean missile threat would be "horrific" but allowing Pyongyang to develop the capability to launch a nuclear attack on the United States is "unimaginable".

There is growing concern that Beijing was steadily eroding the "one country, two systems" principle put in place after it took control of the Asian financial hub.

More than 1,000 protesters walked and chanted in front of China's defence ministry today, the latest apparent demonstration by soldiers as the world's largest standing military modernises and downsizes.

China's military has honoured the pilot missing and presumed dead after a collision with a US spy plane.

The collision that started the spy plane crisis in China occurred after a Chinese F-8 interceptor flew directly below the US aircraft.