Germany's foreign minister on Thursday said the international community remains determined to prevent Iran from developing technology for nuclear weapons despite U.S. assessments that it has stopped working on an arms program.

Foreign Minister Frank-Walter Steinmeier spoke before a briefing by Mohamed ElBaradei, the chief of the International Atomic Energy Agency, on ElBaradei's recent meeting with top Iranian leaders on the nuclear standoff.

Germany and the five permanent Security Council members plan to meet Tuesday in Berlin for talks that diplomats said will include attempts to iron out differences on the language and timing of a third set of U.N. sanctions for Tehran's refusal to freeze uranium enrichment and meet other council demands.

"The conflict over Iran's nuclear program remains ... on the agenda" despite last month's U.S. intelligence assessment that Tehran stopped active work on a nuclear weapons program in 2003, he said. "The problem is not solved."

Urging Iran to "resurrect international confidence" in its nuclear intentions, Steinmeier said the international community "cannot and will not allow that technology for nuclear weapons be developed in this region."

He was alluding primarily to uranium enrichment, which Iran says it wants to develop to be able to generate nuclear power, but which also can create the fissile core of nuclear warheads. Iran refuses to mothball the program despite two sets of U.N. sanctions.

Opposition from Russia and China to quick and harsh new sanctions has increased in the wake of the U.S. intelligence estimate. But Steinmeier papered over differences, saying the Berlin meeting will focus on making sure that international unity over the need for Iran to heed Security Council demands" will continue to be expressed in the future."

He said that he wanted ElBaradei's assessment of the talks in Tehran "so that we have a substantial discussion" at the Berlin meeting.

The U.S. State Department said Wednesday Washington had no plans to change its sanctions strategy in dealing with Iran.

"The whole strategy here is to use various kinds of diplomatic pressure at a gradually increasing rate to try to get a different set of decisions out of the Iranian leadership," spokesman Sean McCormack told reporters.

Officials commenting on ElBaradei's trip to Tehran last week said Iran had promised the U.N.'s chief nuclear inspector to answer all remaining questions about its past nuclear work within four weeks, including secret activities the U.S. suspects were linked to a weapons program.

The probe originally was slated to be completed in December, and the United States and its allies have been chafing at the delay, say diplomats accredited to the IAEA. But they are unlikely to object publicly if the extension allows ElBaradei to reveal details of such secret programs.

In agreeing to the IAEA probe last year, Iran agreed to answer all lingering questions about its past nuclear activities — including those it has evaded since 2003, when nearly 20 years of Iranian clandestine atomic work were revealed.

Diplomats have told The Associated Press that the IAEA probe is now using evidence provided by the U.S. and its close allies to back its allegations. One said Sunday that the IAEA recently shared some of the formerly classified information with Iran, with Washington's permission, to aid with the probe.

Among the material is data on a laptop computer reportedly smuggled out of Iran. In 2005, U.S. intelligence said that information suggested that the country had been working on details for nuclear weapons, including missile trajectories and ideal altitudes for exploding warheads.

U.S. intelligence was also shared with the agency regarding the "Green Salt Project" — a plan that the U.S. alleges links diverse components of a nuclear weapons program, including uranium enrichment, high explosives testing and a missile re-entry vehicle.

The IAEA is also interested in activities at a former research center at Lavizan-Shian, which Iran razed before allowing agency inspectors access. The center is believed to have been the repository of equipment bought by the Iranian military that could be used in a nuclear weapons program.