While the United States and Germany said on Saturday they saw no sign of Iranian concessions on its nuclear program and might opt for added pressure, China and Russia once again cautioned against new sanctions.

U.S. Defense Secretary Robert Gates said Iran had failed to address the concerns held by Western countries and suggested it was time for more sanctions.

German Foreign Minister Guido Westerwelle said Iran had so far failed to dispel Western skepticism that it was prepared to make meaningful concessions over the country's nuclear program.

Top officials from the five permanent members of the United Nations Security Council plus Germany attended the Munich Security Conference on Friday to discuss how to better persuade Iran to halt its nuclear enrichment program which Western countries fear could turn to nuclear weapons production.

But Chinese Foreign Minister Yang Jiechi attending the meeting urged the international community to be patient and keep up diplomatic efforts with Iran.

Russian Foreign Minister Sergei Ivanov said in Munich that any sanctions against Iran should focus on stopping nuclear proliferation rather than on targeting its economy.

Diplomatic efforts have been aimed at persuading Iran to send its low enriched uranium to a mutually-agreed third party for further processing into reactor fuel. There has been a proposal Iran send its low enriched uranium abroad in exchange for higher-grade fuel to be used in making medical isotopes.

Enrichment outside Iran is part of a UN-brokered deal Western countries are pushing hard for.

The West has accused Iran of using its nuclear program to develop a nuclear weapon, a charge adamantly denied by Iran, which insists its nuclear program is for peaceful purposes only.

Iranian Foreign Minister Manouchehr Mottaki described his discussion on Saturday with the head of the International Atomic Energy Agency (IAEA) as "a very good meeting."

IAEA Director-General Yukiya Amano said he wanted the dialogue with Iran to speed up.

"Dialogue is continuing. This should be accelerated. That's the point," Amano said.

An agreement on exchanging low enriched uranium for fuel would come as a relief for Western countries that fear Iran could use enriched uranium to make an atomic bomb.

"I don't have the sense that we're close to an agreement," said Gates, who travelled to Ankara over the weekend for talks with Turkish leaders.

Iranian foreign minister Mottaki said after talks with the IAEA chief that his country might want to exchange less than the 1,200 kilograms of uranium that Western countries have been demanding to be sent away all at once.

"We determine the quantity on the basis of our needs and we would inform the parties about our requirements," Mottaki said.

While some analysts were mixed on the various messages from Tehran since Iran's presidential election last year, the United States believes that it is still the "old game" "playing for time."

U.S. National Security Advisor James Jones said Iran's "puzzling defiance" over its nuclear enrichment program compelled Washington and allies into considering added pressure.

EU foreign affairs chief Catherine Ashton said Iran's response has gone "without adequate response," referring to the Chinese foreign minister's call for more diplomatic efforts with Iran.

"I agree with the Chinese foreign minister that the possibilities of dialogue are not exhausted, but dialogue takes two," Ashton said.