PARIS (AP) The U.N. Security Council's five permanent members and Germany are expected to agree Tuesday on a new resolution to pressure Iran over its nuclear program, a French diplomat said. But a U.S. official said differences over the issue remain.

The senior French diplomat, who briefed reporters Monday on condition that he not be identified by name, said an agreement was very close and should be finalized by the six nation's foreign ministers at a meeting in Berlin, Germany.

However, others were more cautious about what the talks could produce. Momentum for a third resolution has slowed since a U.S. intelligence assessment last month indicated Tehran had stopped active work on a nuclear weapons program in 2003.

A senior US official said Monday that the six nations had made some progress in negotiating a new resolution in a flurry of weekend conference calls but that "substantial" differences still existed.

The official, speaking on condition of anonymity due to the sensitivity of the ongoing talks, told reporters it was not clear if agreement could be reached at Tuesday's meeting.

The official said senior negotiators from all six nations would have another conference call ahead of the ministerial meeting in Berlin.

The French diplomat would not give details on the resolution but said it would be "very balanced, very firm" and likely be presented to the U.N. Security Council at the end of the month.

"We are really very close," said the diplomat, who spoke on condition of anonymity because the talks are ongoing and sensitive.

Any new agreement would need Security Council approval. It already has issued two resolutions on Iran imposing international sanctions over its defiance of international demands that it suspend uranium enrichment. The United States, Britain, France, Russia, China and Germany have been discussing for months a third U.N. resolution.

German Chancellor Angela Merkel said last week that negotiations on a third sanctions resolution have been "slowed down a little bit" as a result of the U.S. National Intelligence Estimate.

Opposition from Russia and China to quick and harsh new sanctions has increased since the U.S. report, but Western nations have stressed the need to keep up the pressure.

Iran insists it never had a weapons program and that its uranium enrichment is aimed at energy production.

Francois Gere, an Iran specialist and head of the French Institute of Strategic Analysis, said he was "a little skeptical" that a third resolution would gain Russian and Chinese approval so quickly. There has been little sign of progress in recent weeks.

He suggested the French announcement could be a pressure tactic ahead of Tuesday's talks. France pushed vocally late last year for tough new sanctions and "does not want to give the impression of pulling back now," Gere said.

Iranian Foreign Ministry spokesman Mohammad Ali Hosseini said Monday that Washington and the other Western powers will not succeed in efforts to halt Iran's nuclear program.

"They are looking for excuses," he said. "This will not bear fruit and will mostly work against them and we will continue our constructive cooperation with the (International Atomic Energy) agency," the U.N. nuclear watchdog.

Earlier in January, IAEA director Mohammed Elbaradei visited Tehran, and Iran agreed to answer all remaining questions over its nuclear activities in the next few weeks.

Iran's nuclear negotiator, Saeed Jalili, will be in Brussels on Wednesday to talk at the European Parliament, but the EU's Solana said that, as yet, they have no plans to meet.

"I have to see if that is a real use of my time, for me to meet him," Solana told reporters on Monday. "We may find some time to meet."

Washington AP reporter Matthew Lee contributed to this report.