The United States voiced deep concern on Thursday at reports that China is dramatically scaling up its nuclear arsenal, urging Beijing to engage in talks to avoid a global arms race.

"It is in everyone's interest that nuclear powers talk to one another directly about reducing nuclear dangers and avoiding miscalculation," Robert Wood, US ambassador to the Conference on Disarmament in Geneva, told reporters.

Last week, the Washington Post newspaper cited a study of satellite images that it said showed 119 silos for missiles were being built in a desert near the northwestern city of Yumen.

The silos, according to the report, were similar to existing Chinese launch facilities for nuclear-tipped ballistic missiles.

Wood said it was of "great concern".

"Until China sits down with the United States bilaterally, the risk of a devastating arms race will continue to increase, and that is in the interest of no-one," he said.

China, he said, claimed to be "a responsible nuclear power" with only a very small defensive arsenal.

"But when we see a lot of what China has been doing, it runs counter to what it has been saying."

Stockpile worries 

Wood highlighted a range of new systems China was believed to be looking to develop, including missiles capable of hitting the United States.

He said these kinds of systems had "great potential to change the entire dynamic of the global strategic stability situation". 

Wood said one of the biggest problems was a lack of transparency, since China does not divulge details about its arsenal.

In its first public estimate of China's nuclear capacity last year, the Pentagon said China appeared to have more than 200 nuclear warheads, and cautioned that Beijing seemed to be pushing to double that number within the next decade.

"We say that the nuclear weapons programme is likely to double its stockpiles in the next 10 years, but it could be greater than that," Wood warned.

"Without it sitting at the table, it's hard to say what China is actually doing."

China's estimated stockpile still remains a far cry from the more than 11,000 nuclear warheads owned by the United States and Russia put together.

But Wood dismissed arguments that before any discussions with China could take place, the world's two largest nuclear powers should shrink their arsenals to China's level.

"With the US and Russia, we've had, over the years, frameworks for addressing these issues," he said.

"We don't have such frameworks with China."