"We continue to have some tactical differences about the timing, but more than that, about how deep this (UN) resolution should go," Rice said in an interview with AFP after senior diplomats from the six powers consulted Thursday.

The United States has been involved in difficult talks with Russia, China, Britain and France -- the five permanent UN Security Council members, or P5, that all have veto power -- and Germany for another UN resolution against Iran.

Washington is promoting a two-track strategy aimed at offering Iran a dialogue that would give it economic benefits if it stops enriching uranium, or at threatening a third round of punitive sanctions.

The political directors of the State Department and the foreign ministries of the five other countries did not reach agreement during a conference call Thursday, but Rice said they agreed on the broad approach.

She stressed what she called "forward movement" in the talks.

"I suspect that at some point this is going to have to go to ministers, as it always does. But we think that there's enough continuous forward movement, that it's good for the political officials to keep talking," she told AFP.

"We are all in agreement that the two-track strategy that we have been pursuing is the right strategy, because we need to convince Iran that it should stop its enrichment and reprocessing activities," Rice said earlier, in a news conference with her Canadian counterpart Maxime Bernier.

"Enrichment and reprocessing is, after all, the long pole in the tent, because that's how one gets fissile material that can either be used in civilian programs, but can certainly be used in a nuclear weapons program.

"And so, that is why the world has been focused on that in two separate Security Council resolutions," Rice said.

The political directors of the six countries held a 90-minute conference call on December 11 about Iran's nuclear program, but did not finalize a draft sanctions resolution.

Rice admitted afterward that the United States has "tactical differences" with Russia and China about the "timing, about the nature of any further sanctions."

But she said that "the two-track strategy remains in place," when asked if the US National Intelligence Estimate, published December 3, undercut the US drive for sanctions.

The report said Iran had stopped an alleged covert nuclear weapons program in 2003. Iran insists its nuclear program is peaceful.

Rice conceded that China's key trade ties with Iran was a "sticking point" in efforts to get Beijing's support for sanctions. The Asian giant is a major importer of Iran's oil and gas.

"Obviously, the Chinese have some economic interests that are different from the economic interests of the other parties. And that is, frankly, sometimes a sticking point," she told AFP.

"But I think we'll still get a good resolution."

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