SINGAPORE - US Defence Secretary Robert Gates on Sunday offered China briefings on the US missile defence system to reassure them that it does not threaten China's nuclear deterrent.

His remarks, at the end of a two-day conference on Asian security, followed a top Chinese general's criticism of defences being developed by the United States and Japan to protect against North Korean missiles.

"I'm not sure why they are so worried," Gates said. "Just as with the Russians, we would be pleased to sit down with them and talk about the capabilities and technical characteristics of this system and its limitation.

"There may just not be a clear understanding on the part of the Chinese about what we have in mind can and cannot do," he said.

Lieutenant General Zhang Qinsheng, the chief of military intelligence of the People's Liberation Army, objected to the US-Japanese missile defence project in a speech Saturday at the Shangri-La Dialogue on regional security issues.

Zhang's concerns echo those of Russia, which fiercely opposes US plans to deploy interceptor missiles in Poland and radar in the Czech Republic to protect against missiles from Iran.

To overcome Moscow's opposition, Gates in April offered the Russians what he said was an unprecedented partnership in missile defence and inspections sites in Alaska and California.

Asked whether the United States would offer the same to China, Gates told reporters, "I think if the Chinese were to express an interest in it we would certainly take it seriously."

He said the US system was designed to thwart limited attacks by rogue states or terrorists, not to defeat a large-scale threat of the kind posed by the long-range missile arsenals of Russia and China.

"So anything we can do to provide transparency on that point and help people understand the capabilities and characteristics of these systems, we're prepared to do it," he said.

Gates is trying to encourage greater interaction with the Chinese military, in part to avoid miscalculations as it undertakes a major build-up of its forces.

Zhang said China was prepared to establish a "hotline" between the US and Chinese defence ministries, meeting a long-standing US objective, and that China was making gradual progress on US demands for greater transparence.

But mistrust between the two countries is high.

A Pentagon report last week detailed China's push to acquire advanced warships, submarines, aircraft and missiles, saying it would allow China to project power far beyond its shores and alter regional military balances.

Zhang, who called the Pentagon report "unreliable," raised it on the sidelines of the conference with General Peter Pace, the chairman of the Joint Chiefs of Staff.

"The Chinese are not happy with our depiction of their armed forces," Pace said.

"I recommended that they invite the authors of the report to China to sit down and have discussion about what it is they think we see about them that they don't see about themselves. And just get it on the table, in a very open way, for discussion," he said.

"The way ahead from my standpoint is more discussion, more transparency, if they want to have an impact on reports in the future," he said.