SEOUL, South Korea (AP) - President Barack Obama said Thursday that the six nations dealing with Iran's nuclear program will develop a package of serious new punitive measures in coming weeks. The European Union said the six would gather immediately to begin consultations.

The EU said diplomats would meet in Brussels Friday to consider Iran's apparent rejection of a U.N. plan to ship its low-enriched uranium abroad so that it could not be further enriched to make weapons. Talk of sanctions showed that Obama is preparing for the next phase should Iran fail to meet his year-end deadline for progress in negotiations.

The Brussels meeting will include the U.N. Security Council's permanent members - Britain, China, France, Russia and the U.S. - plus Germany, EU foreign affairs spokeswoman Cristina Gallach said. She said it would bring together foreign ministry officials from the six nations "to take stock of the situation."

Iran announced on Wednesday it would not export its enriched uranium for further processing, effectively rejecting the latest plan brokered by the International Atomic Energy Agency. That plan aimed to delay Tehran's ability to build a nuclear weapon by sending most of the uranium needed for that out of the country.

Under the plan, Iran would export its uranium for enrichment in Russia and France where it would be converted into fuel rods, which would be returned to Iran about a year later. The rods can power reactors but cannot be readily turned into weapons-grade material.

President Barack Obama said Washington has started talking with its allies about new punishments against Iran.

"They have been unable to get to 'yes', and so as a consequence, we have begun discussions with our international partners about the importance of having consequences," Obama said at a news conference in Seoul. "Our expectation is, is that over the next several weeks we will be developing a package of potential steps that we could take that will indicate our seriousness to Iran."

In talking tough about possible sanctions on Iran for its nuclear program, Obama left open the option that diplomacy could still work. "I continue to hold out the prospect that they may decide to walk through this door" and accept the proposal to ship its low-enriched uranium out of the country, Obama said.

A senior administration official later said Obama was purposely vague on more diplomacy so as not to undermine the search for international consensus that remains in an embryonic phase. The official spoke on condition of anonymity to discuss the president's thinking.

The United States and other nations fear Iran wants to build nuclear arms, but Tehran insists its nuclear program is peaceful.

"Yesterday, Iran clearly refused the deal," French Foreign Ministry spokesman Bernard Valero said Thursday. "We are going to evaluate with our partners ... the consequences of this political response."

Any new sanctions would probably take months to enact. China, always reluctant to support sanctions, offered no assurances that it would agree to punish Iran.

Iranian Foreign Minister Manochehr Mottaki played down the threat of sanctions, saying embargoes have proved ineffective in the past.

"I think they are wise enough not to repeat failed experiences," Mottaki told reporters Thursday in Manila.

In a related development, diplomats in Vienna said IAEA inspectors paid a second visit to Iran's recently revealed Fordo uranium enrichment facility on Thursday.

Iran acknowledged Fordo's existence in September in a confidential letter to the U.N. watchdog, then faced sharp criticism from the U.S., Britain and France for hiding the facility for years. Iran says it is building the fortified facility as a backup in case its main plant at Natanz is attacked.

The diplomats spoke on condition of anonymity in exchange for divulging confidential information.

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Lekic reported from Brussels. AP reporters Vladimir Isachenkov in Moscow, Jenny Barchfield in Paris, Oliver Teves in Manila, George Jahn in Vienna and Deb Riechmann in Kabul contributed to this report.