Seoul (S. Korea), Nov. 19 : US President Barack Obama said Thursday the United States has begun talking with allies about fresh punishment against Iran for defying efforts to halt its nuclear weapons pursuits.

Obama''s tough talk came as Iran indicated it would not ship its low-enriched uranium to Russia for processing, the centerpiece of deal aimed at a peaceful resolution of Iran''s contested nuclear program.

Obama advanced the prospect of sanctions but held out the option of diplomacy.

He said Iran must get a "clear message" and described a "package of potential steps that we could take that will indicate our seriousness to Iran."

"I continue to hold out the prospect that they may decide to walk through this door," Obama said, although US hopes for agreement with Iran were dimming. 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 in a brief news conference with South Korean President Lee Myung-bak.

Obama said a new package of punitive steps will likely be developed "over the next several weeks."

According to CBS, he did not get more specific about the nature of any new sanctions, which would require commitments of international support that are hardly clear yet.

President Lee also signaled his government''s impatience over another nuclear threat, North Korea.

Both declared new, united steps in getting Pyongyang to give up its own nuclear weapons.

Lee and Obama both supported Seoul''s idea of a one-time "grand bargain" with North Korea of aid and concessions in exchange for de-nuclearization, rather than the stalled step-by-step process. (ANI)