The EU governments' sanctions target major Iranian state companies in the oil and gas industry, and strengthen restrictions on the central bank, cranking up pressure on the country which has close trade ties with Beijing.

China is Iran's largest crude oil customer and, along with Russia, has resisted putting sanctions on Tehran.

"We oppose the imposition of unilateral sanctions on Iran and believe that using sanctions to exert pressure cannot fundamentally resolve the Iran nuclear issue," Chinese Foreign Ministry spokesman Hong Lei told a daily news briefing.

"It can only make the situation more complex and intensify confrontation... We hope that all relevant parties can show flexibility, increase communication and push for a new round of talks as soon as possible."

EU foreign policy chief Catherine Ashton, who represents the United States, China, Russia, Britain, France and Germany in their on-and-off talks with Iran, said on Monday she hoped turning up the heat on Iran would persuade it to make concessions and that negotiations could resume "very soon".