Washington: China does not want to see Iran develop nuclear weapons but intends to pursue its "legitimate economic interests" despite Western sanctions on the Islamic republic, an official said.

Vice Foreign Minister Cui Tiankai, accompanying China's Vice President Xi Jinping on a weeklong visit to the United States, said the two sides had discussed "hot spot" issues like Iran's controversial nuclear programme.

"We call for efforts to maintain the effectiveness of the international non-proliferation regime and to maintain peace and stability in the region," he told reporters at a briefing in Washington late on Tuesday.

"As for relevant Security Council resolutions on sanctions, we voted for these resolutions and we have been enforcing them most strictly. But we do have reservations on unilateral sanctions and this is nothing new."

He added that "with regard to Iran... the legitimate economic interests and energy demands of China should not be affected."

The United States and the European Union have ratcheted up economic sanctions on Iran to an unprecedented level to try to force it to halt its uranium enrichment program and re-engage in long-stalled talks.

The latest measures go beyond four rounds of UN sanctions placed on Iran in recent years, and come as a stream of media reports have suggested Israel may carry out a military strike on Iranian nuclear facilities later this year.

The United States and Israel have accused Iran of secretly pursuing atomic weapons, charges denied by Tehran, which insists its nuclear enrichment program is for purely peaceful purposes.

Beijing's economic ties with Iran, a major oil exporter, have expanded in recent years, partly thanks to the withdrawal of Western companies in line with the sanctions.