New York - Diplomats from six key powers focused on possible new sanctions against Iran over its nuclear program at a meeting Saturday, but reached no agreement.

Robert Cooper, the European Union's political director who chaired the meeting, said the U.S., Russia, China, Britain, France and Germany concluded "that Iran has failed to follow up" on an agreement in principle in October that Tehran exchange uranium for nuclear fuel, "in particular by refusing further meetings to discuss the nuclear issue."

Russia's Deputy Foreign Minister Sergei Ryabkov said the six powers "reconfirmed our desire" to meet again with the Iranians to discuss their October proposal.

"We have talked mostly today on the second track, but it doesn't mean that we should abandon the first one," he said.

But a senior diplomat, speaking on condition of anonymity because the talks were private, said the message to Iran from the meeting is that time is running out.

Iran argues that its nuclear program is aimed at creating a peaceful nuclear energy network to serve its growing population. The U.S. and other nations believe Iran's nuclear program has the goal of creating atomic weapons.

The United States and its Western allies have been pushing for a fourth round of U.N. sanctions. But with Russia, and especially China, skeptical of any new sanctions, they have to tread carefully to maintain six power unity on how to deal with Iran.

The senior diplomat said there would be further meetings of the six countries but no date has been set.

Saturday's meeting was supposed to be of political directors - top diplomats in the countries' foreign ministries - but China was only represented by a counselor from its U.N. mission, Kang Yong, not Vice Foreign Minister He Yafei.

Taking over the rotating presidency of the Security Council in early January, China's U.N. Ambassador Zhang Yesui said Beijing opposes new sanctions against Iran for now because diplomatic efforts to bridge differences over the country's nuclear program are taking place.

China - which relies on Iran for much of its energy - is a veto-wielding member of the Security Council along with the U.S., Russia, Britain and France.

Zhang's opposition means the council almost certainly won't discuss Iran sanctions in January, but whether they may be open to future sanctions talks remains to be seen.

Cooper said Saturday's meeting was "for stock-taking and to see the way ahead."

Russia's Ryabkov said "the meeting is inconclusive in a sense that we didn't make any decisions right away."

"We have started the next chapter of this saga. We have started the next part of the process," he said. "We made a lot of progress."

U.S. Undersecretary of State William Burns told reporters as he left the talks that it was "a good meeting."

The diplomats refused to disclose what possible sanctions were discussed.

U.S. Secretary of State Hillary Clinton said Monday that the Obama administration has concluded that the best way to pressure Iran to come clean on its nuclear ambitions is to impose new sanctions aimed at the country's ruling elite.

One well-informed diplomat said recently that the Revolutionary Guard would be a key target of a fourth round of sanctions, but others in Iran's power structure could also be included. Sanctions against companies and organizations controlled by the Revolutionary Guard that have links to weapons proliferation may also be considered, the diplomat said, speaking on condition of anonymity because all talks are going on in private.

The Security Council would likely ban travel and freeze the financial assets of individuals, and freeze the assets of any companies.

Cooper said the six powers are concerned that Iran has been secretly building a uranium enrichment facility near Qum "with no credible civilian purpose" and without notifying the International Atomic Energy Agency, the U.N.'s nuclear watchdog.

They are concerned at Iran's "insufficient cooperation with the IAEA" and with its response to a resolution adopted by the agency's board of governors on Nov. 27 which demanded that Tehran immediately stop building the Qum facility and freeze uranium enrichment.

The six nations are also concerned "at Iran's failure to take up the IAEA proposed agreement" to ship most of its uranium - up to 2,600 pounds (1,200 kilograms) - abroad.

The uranium would then be enriched to higher levels in Russia, turned into fuel rods in France and returned to power a research reactor in Tehran that produces medical isotopes. The material in the fuel rods cannot be enriched to higher levels, denying Iran the ability to use it to make weapons.