US Defence Secretary Robert Gates appealed to China for help in curbing Iran's nuclear programme, arguing that a stable Gulf was in the interests of Beijing's energy security.

Gates said he raised the issue of Iran in his meetings with Chinese defence and foreign ministry officials, although it did not come up during talks with President Hu Jintao on Tuesday, which he said focused on military relations.

"An Iran that is a destabilising force in the region is not in anyone's interest, including in China's," Gates said as he toured the Forbidden City.

"If one is interested in long-term energy security, then a stable Persian Gulf, Middle East area is a very high priority."

Both the US and China are veto-wielding members of the UN Security Council.

But while Washington is seeking tougher UN sanctions on Iran, China -- which sources about 12 per cent of its oil there -- favours talks to resolve the issue of its nuclear programme.

Tehran says its atomic programme is purely for energy generation and has refused to halt uranium enrichment after two previous UN sanctions resolutions. Washington believes Iran is trying to produce a nuclear bomb.

Gates said he also hoped his talks in China would lead to a long-term dialogue to resolve issues between the two countries over transparency and China's military buildup.

"I hope what will come out of it is an ongoing dialogue about these (issues). It's not a matter of just raising it and each side sort of having a set-piece response," he said.

On Monday, the two sides agreed to set up a hotline following talks that both described as "candid", but they remained at odds over the scope of China's military modernisation and an anti-satellite test.Reuters