China is expected to announce its biggest military budget increase in nearly a decade in the next couple of days, fuelled by increasing tensions in the South China Sea and the need for the latest weaponry.

Key points: China's military insiders say the budget could increase by up to 20 per cent

China's military insiders say the budget could increase by up to 20 per cent Increase will fund massive reform program for China's army

Increase will fund massive reform program for China's army US says it will step up patrols in the area, says increasing militarisation of South China Sea will have consequences

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The increase is set to worry countries in the region, who see the massive rise as a driver for an Asian arms race.

China's military insiders say the budget could increase by up to 20 per cent. Last year the budget was $200 billion.

"The Chinese Government is not only determined but capable of continuously increasing the military budget," Professor Shi Yinhong from the Renmin University of China said.

"In the arms race in the Western Pacific, China wants to close the gap with the US."

The increase will fund a massive reform program, which will make the People's Liberation Army a meaner and leaner fighting machine.

The world's largest army has cut 300,000 soldiers and money is needed to pay them out.

On top of this, to keep morale and loyalty up, President Xi Jinping will hand out a pay rise.

But the lion's share of the budget will have been spent on updating and modernising China's weaponry.

"The most expensive part will be the advanced weapon systems — the missile systems," Professor Shi Yinhong said.

"If we describe China's defence expenditure as a sword, the sharp point are these systems."

Tensions in the South China Sea are also driving the increase, and much of the modernisation drive will be directed into China's navy, which is critical to enforcing territorial claims.

Regional countries fear the massive increase in China's armed forces will further fuel an Asian arms race.

The US has said it will step up its patrols in the area, and has warned China that its increasing militarisation of the South China Sea will have consequences.

China maintains it is just looking after its interests and is ready to respond..

Hawks driving policy on both sides

Jia Qingguo, a professor of international relations from Peking University, said the problem was that hawks from both sides were now in control.

"China is a rising power. The US is an established power," Professor Qingguo said.

"These two can't get along peacefully so, ultimately, there will be a confrontation. People are pushing this argument, and its affecting the choices of the governments."

Professor Yinhong said China's position on the South China Sea could not be moved.

"The South China Sea is vast," he said.

"China's determination is very strong. As Xi Jinping said, we will not lose one inch of the land left by our ancestors — so China will invest more."

The details of China's military increase will be released at the National People's Congress in the coming days.