SEOUL, South Korea (AP) — President Barack Obama is on his way back to Washington after an Asian tour that included efforts to prod China on human rights and North Korea to return to nuclear talks.

Obama today said the United States has begun talking with allies about fresh punishment against Iran for defying efforts to halt its nuclear weapons pursuits.

During a brief news conference with South Korean President Lee Myung-bak the leaders signaled impatience over another nuclear threat, North Korea. They both declared fresh, united steps in getting that nation to give up its own nuclear weapons.

Obama says his envoy will travel to North Korea next month for the first bilateral talks since he took office.

Before taking off, Obama visited U.S. troops stationed at the Osan Air Base and thanked them for their service.

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Mark Smith

President Barack Obama is heading home after a week-long trip to Asia. AP White House Correspondent Mark Smith reports.

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Sound of traditional Korean music with dancers in ancient costumes

This is the sound of traditional Korean music with dancers in ancient costumes in a welcoming ceremony for U.S. President Barack Obama.

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Sound of a North Korean military band performing American music

This is the sound of a South Korean military band performing American music in a welcoming ceremony for U.S. President Barack Obama.

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Sound of a North Korean military band performing

This is the sound of a South Korean military band performing in a welcoming ceremony for U.S. President Barack Obama.

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President Barack Obama

President Barack Obama says the United States and its allies are ready to help North Korea join the community of nations only if it dismantles its nuclear weapons program.

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President Barack Obama

President Barack Obama says North Korea cannot backtrack on its promises about disarmament.

<> 00:17 "community of nations"

President Barack Obama

President Barack Obama says the United States and South Korea are offering the North a "grand bargain" involving its nuclear weapons program.

<> 00:09 "approach going forward"

President Barack Obama

President Barack Obama says the United States and South Korea have a strategy on how to tackle the issue of the North Korean nuclear threat.

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Mark Smith

President Barack Obama is urging North Korea to accept a new bid to halt its nuclear program. AP White House Correspondent Mark Smith reports.

<> 00:14 "itself less secure"

President Barack Obama

President Barack Obama says the U.S. and its allies will work on developing a package of potential steps that could be taken if Iran chooses not to come to some agreement regarding its nuclear program.

<> 00:08 "seriousness to Iran"

President Barack Obama

President Barack Obama says the U.S. is working with allies on ways to send Iran a 'clear message' about its nuclear program.

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Mark Smith

President Barack Obama says it looks like America and its allies will have to seek sanctions because Iran is rejecting calls to halt its nuclear program. AP White House Correspondent Mark Smith reports.