China is bracing for its second bond default by a central government-owned company, offering one of the biggest tests yet of Beijing's willingness to impose market discipline on lossmaking state groups.

A unit of one of the elite club of 112 big enterprises directly owned by the central government, China National Erzhong Group employed a workforce of more than 13,000 in 2012, when it had assets of Rmb25bn. But a slowing economy saddled with industry overcapacity has hobbled the heavy industry group, leading to losses of Rmb8.4bn in 2014.

Its looming default comes just a week after Beijing unveiled guidelines for an overhaul of state-owned enterprises aimed at improving their financial performance. SOEs control broad swaths of the economy but are heavily indebted and trail their privately owned counterparts in efficiency and profitability.