UNITED NATIONS (AP) – Iran is “thumbing its nose” at the international community by expanding its uranium program, a top American official said, setting the stage for difficult negotiations on new U.N. sanctions, with the U.S. likely to push for tougher measures.

In the wake of the U.N. nuclear agency’s confirmation that Iran expanded its uranium enrichment program, senior diplomats from the five permanent Security Council nations and Germany will meet on Monday in London to start work on a new resolution to try to pressure Iran to suspend that program, which can lead to the production of nuclear weapons.

Among the permanent council members, Britain and France are likely to join America in a call for harsher sanctions than Russia and China will accept.

Some diplomats said the new measure may invoke travel bans, expand the list of technology and materials countries are banned from making available to Iran and create stiffer economic sanctions, among other options.

Iranian President Mahmoud Ahmadinejad vowed Friday that Iran would defend its nuclear program, describing his country as a potential role model for others trying to develop advanced technology.

“The Iranian nation has resisted all bullies and corrupt powers and it will fully defend its all rights,” State television quoted Mr. Ahmadinejad as telling people in the northern Iranian town of Fuman.

Mr. Ahmadinejad declared that if his country reaches the “peaks of technology and science, then it will be a role model” for other countries, state television quoted him as saying in an apparent reference to nuclear power.

American Undersecretary of State Burns, who announced the London meeting in Washington, said Thursday that Iran was “effectively thumbing its nose at the international community” and a new resolution was needed to “see Iran repudiated again.”

He said, however, that it was too soon to say what provisions the resolution might contain.

Russia’s U.N. Ambassador Vitaly Churkin said he had “no substantive comment” on the International Atomic Energy Agency’s report Thursday which concluded that “Iran has not suspended its enrichment related activities” as the Security Council demanded in a resolution adopted on Dec. 23. But he reiterated Moscow’s desire for a diplomatic negotiated solution.

“We should not lose sight of the goal – and the goal is not to have a resolution or to impose sanctions,” Mr. Churkin said. “The goal is to accomplish a political outcome.”

The IAEA began probing Iran’s nuclear activities more than four years ago, after revelations of nearly 20 years of secret work that included plans to enrich uranium. Since then, it has made several worrying finds, including Iranian experiments with plutonium, unexplained traces of enriched uranium, and a document showing how to mold uranium into the shape of nuclear warheads.

Last June, the six nations offered Tehran a package of economic incentives and political rewards if it agreed to consider a long-term moratorium on enrichment and committed itself to a freeze before negotiations on its nuclear program. Tehran refused to comply with an Aug. 31 deadline to suspend enrichment, insisting its program is aimed solely at producing nuclear energy.

The Security Council responded by unanimously adopting a resolution on Dec. 23 after two months of tough negotiations imposing sanctions on Iran for refusing to suspend enrichment. It ordered all countries to stop supplying Iran with materials and technology that could contribute to its nuclear and missile programs and to freeze assets of 10 key Iranian companies and 12 individuals related to those programs.

The council warned it would adopt further nonmilitary sanctions if Iran refused to comply and that is what members will now be considering.

During negotiations on the December sanctions resolution, the American administration pushed for tougher penalties but Russia and China, which both have strong commercial ties to Tehran, and Qatar, across the Persian Gulf from Iran, balked.

To get their votes, the resolution dropped a ban on international travel by Iranian officials involved in nuclear and missile development and specified exactly which items and technologies were banned.

Several council diplomats have stressed the importance of maintaining council unity on a new resolution – even if means sacrificing tougher sanctions.

Stressing the importance of unity, American deputy ambassador Jackie Sanders said Thursday “we do need to ratchet up the pressure and Iran needs to see an international community that stays coordinated and showing common purpose to have them stop what they’re doing in developing nuclear weapons.”

French Foreign Minister Philippe Douste-Blazy echoed the importance, saying, “unity and firmness are … the only effective instruments we have to get Iran to turn toward the international community, and away from isolation.”

“We support a second resolution, to be passed unanimously by the Security Council, to continue sanctions,” he said.

Two diplomats, speaking on condition of anonymity because negotiations haven’t even started, spoke of an “incremental” strengthening of sanctions in a new resolution to ensure that unity is preserved.

Diplomats said Thursday that new measures under consideration include a mandatory travel ban against individuals on the U.N. list, new individuals and companies subject to sanctions, additional prohibited items, economic measures such as a ban on export guarantees to Iran, and an expansion of the nuclear embargo to an arms embargo.

The permanent council members believe the initial sanctions have had some positive effects. Iran now says it wants negotiations, though it still refuses to suspend enrichment.

Whether new sanctions can bring Tehran to comply with the council’s demands remains to be seen.

“It’s Iran’s refusal to talk which right now has gotten Iran in a lot of hot water,” said Mr. Burns, the American State Department official. “Iran is increasingly isolated, and we hope Iran is going to choose negotiations.”