China has passed its first-ever law on deploying its military which allows troops to take over businesses and other civilian resources and provides for conscription in times of national emergency.

While China's vast military machine has always been under the direct command of the ruling Communist Party rather than the government, the new law leaves no room for any doubt, officials say.

The law would be useful in times of war and during social unrest as occurred in the regions of Tibet and Xinjiang in recent years, General Bai Zixing told reporters, as well as when the military is needed during natural disasters.

"Although our army is the party's army, it is also the people's army," Bai said on Friday.

"This law brings together the will of the party and the will of the state (to mobilise) the army to safeguard state security and unity and safeguard social stability."

The bill was passed by the standing committee of the National People's Congress, China's parliament, ahead of the opening next week of the annual meeting of the full legislature, congress spokesman Han Ke told reporters.

According to the law, the standing committee will declare military mobilisation at times of state emergencies or security threats, following which the president must issue a mobilisation order.

The law was passed at a time of major expansion and modernisation of China's massive armed forces, which has raised concern overseas about Beijing's military intentions.

The law also stipulates subsidies and preferred treatment to companies that make products for national defence and lays out regulations for the military to expropriate civilian resources.

Beijing has announced a series of double-digit military budgets throughout most of the past two decades and will announce its 2010 budget during the full congress in March.

The United States and some of China's regional neighbours have expressed concern about the build-up, which Beijing stresses is defensive in nature.