China said Tuesday it was growing more concerned over the Iran nuclear crisis but again resisted calls to back sanctions, insisting talks were the best way to resolve the impasse.

Visiting British Foreign Secretary David Miliband, who is seeking Beijing's support for tougher UN sanctions against Iran, voiced his increasing impatience with the Islamic republic.

Chinese Foreign Minister Yang Jiechi pledged after talks with Miliband that Beijing would work more closely with other world powers on Iran, which is suspected by the West of secretly trying to develop the atomic bomb.

"Regarding the Iranian nuclear issue, I wish to point out that this issue is the subject of widespread attention in the international community. China has become more concerned about the current situation," Yang told reporters.

Miliband, who met later with Premier Wen Jiabao, had tough words for Tehran, noting an increasing "lack of confidence in the international community as to Iranian intentions".

He said Iran "can be treated as a normal country on nuclear matters when they behave as a normal country".

But Yang gave no sign that China would bend to mounting pressure to support a new round of sanctions on Tehran, which insists its nuclear programme is for peaceful energy needs.

"Ultimately, this issue has to be appropriately resolved through peaceful negotiations," Yang said.

Britain, alongside the United States and its allies, is pushing for the UN Security Council to impose tougher sanctions but China is the only veto-wielding permanent member not backing further punitive action.

China is a major ally of Iran and now its top trading partner as a key buyer of its energy resources. In the past, it maintained a similar stance on sanctions, only to eventually acquiesce to watered-down measures.

But Yang indicated China's willingness to work more deeply with world powers spearheading the drive to contain Iran's nuclear drive.

"We will have even closer contact with members of the P5+1 mechanism and other related parties," he said, referring to the five permanent Security Council members plus Germany.

"We will continue to make efforts to bring about a diplomatic solution to the Iranian nuclear issue," Yang said.

The two foreign ministers pledged to work together to strengthen diplomatic ties after the two nations clashed on human rights and global warming as well as their differences on Iran.

During Miliband's meeting with Wen, the Chinese premier said ties between the two countries were strong and called for an even deeper relationship, state television said in a brief report.

Miliband told reporters that during his talks with Yang he raised the case of Gao Zhisheng, a human rights lawyer whose whereabouts China refuses to divulge after he was taken away by police more than a year ago.

Gao had been on probation after being convicted of subversion in 2006.

Yang denied Gao had been tortured or had his rights violated, but provided no further information on him.

Relations between Beijing and London soured last year when Miliband's younger brother Ed, the British climate change secretary, accused China of "hijacking" a Copenhagen summit on global warming.

Britain was also furious at China's execution in December of a Briton on drug smuggling charges.

"I come here in the spirit of partnership as we face common challenges together," said Miliband.

Yang said relations were "developing in a positive direction", adding: "We are committed to working with Britain to advance the comprehensive strategic partnership."