China's decision to shelve a series of planned copper smelters is unlikely to have an impact on historically tight markets unless it is followed by more measures to curb output in the world's largest refined copper producer, industry insiders said.

The relentless growth of Chinese smelting capacity has increased global competition for copper concentrate feedstock at a time when stretched supplies have become scarcer still due to mine disruptions.

Fees paid to process copper, known as treatment and refining charges, have fallen to historic negative levels. In a nod to the bind facing Chinese smelters amid annual negotiations for copper concentrate supplies, China said on Wednesday it had suspended work on 2 million metric tons of planned new smelting capacity.

But there will likely be no immediate effect on copper markets, said eight analysts and three traders, who spoke with Reuters on the sidelines of the World Copper Conference Asia in Shanghai this week, given that projects already under construction are expected to be completed.

“I don't think the decision in itself is going to change anything in the next couple of years, because we're still seeing a wave of new smelting capacity coming on stream," said Helen Amos, a commodities analyst at BMO Capital Markets.

One Chinese analyst, speaking on condition of anonymity, said the announcement, which did not name any projects, only raised more questions, including how the figure of 2 million tons was calculated.

The Chinese government has renewed its focus on reversing rampant industrial overcapacity. Coal, lithium and the solar panel raw material polysilicon have all been targeted with policies to reduce output.

It remains unclear, however, how far Beijing will go to rein in a sector whose production helps offset the refined copper imports on which China relies and would like to reduce.

If Wednesday's decision signals it is considering or even planning more drastic measures like forced capacity cuts or a production cap, then the impact could be more significant, the industry figures said.

"For me, it's symbolic that the industry is going to start to be affected by policy change like what we saw in steel and aluminium in the past," Amos said.