US pressures China to condemn North Korea 'aggression'
US Secretary of State Hillary Clinton left Asia after a week of intense discussions in Japan, China and South Korea seemingly empty-handed but sounding optimistic about the prospect of international consensus on a response to North Korea's actions.
But much still depends on the deliberations currently taking place inside the Chinese government about how to handle the dilemma their allies in Pyongyang have presented.
Throughout her trip, Mrs Clinton emphasised that Beijing understood the gravity of the situation and that no-one was more concerned about stability and peace of the Korean peninsula than the Chinese.
She also said it was in everyone's interests, including China, to make a persuasive case for North Korea to change direction.
Mrs Clinton acknowledged that China and the US often saw things from a different perspective.
Washington has been seeking to send a strong signal to North Korea to make clear it cannot get away with the sinking of a South Korean warship.
Beijing has traditionally been reluctant to push Pyongyang. It fears the consequences of instability or regime collapse inside North Korea, with which it shares a border.
But North Korea's actions in themselves have now caused considerable tension in the region, and US officials believe this is giving China some pause for thought.
During her four-hour visit to Seoul, Mrs Clinton said it was in everybody's interests, including China's, to persuade North Korea to change direction.
"I think it's fair to say that China is in the process of looking hard at what its interests are on the Korean peninsula and its positioning vis-a-vis North Korea," said one senior American government official.
But the Chinese will be careful about what they say in public and will avoid looking like they're taking sides with South Korea and by extension the US, because it would look like they have abandoned their ally.
The Chinese have so far refused to criticise North Korea and have only called on all sides to show restraint.
They've also shown scepticism about the results of an international investigation which determined that it was a North Korean torpedo that sank the warship Cheonan in March.
During her trip, Mrs Clinton repeatedly referred to the investigation as "objective" and "scientific" in a clear message to the Chinese, saying the conclusions were inescapable.
During a joint news conference in Seoul, South Korean Foreign Minister Yu Myung Hwan said that "the Russians and the Chinese of course will take their time I'm sure, but they will not be able to deny the facts".
US officials in the delegation to China said they had shared with the Chinese specific information about the sinking of the Cheonan. Several American experts participated in the investigation.
The episode is reminiscent of the time last year when the Americans presented the Russians with evidence that Iran had a secret nuclear facility at Qom.
The Russians were furious that their allies in Tehran had kept this from them and they decided to finally back a further round of UN sanctions against Iran.
"There is substantial debate (in China) about how to proceed on North Korea," another senior US official said.
"I think it began last year with the nuclear missile test. I think it is accelerating now.
"There are discussions within the leadership and outside the leadership, there is profound frustration with North Korean behaviour and the way in which it complicates China's own security calculations."
Neighbouring Japan announced on Sunday that it would not move a US base off the island of Okinawa, despite promises made by Prime Minister Yukio Hatoyama during his election campaign.
After months of negotiations and growing tension between Washington and Tokyo about the Futenma base, fear of instability in the region following North Korea's actions finally prompted Japan to stick to a deal agreed to under a previous Japanese government to relocate the base to a different part of the island.
The American officials said that the US was now working with South Korea to get statements of condemnation from the Association of South East Asian Nations (Asean) - as well as the G8 and the G20 - while helping Seoul in its efforts to bring the issue to the UN.
It's unclear how quickly the UN could take up the issue. The Security Council is currently working to push through a much debated and much awaited resolution imposing further sanctions on Iran.
Introducing a resolution on North Korea before the Iran vote is sealed may muddy the waters.
On both issues, the US needs China's backing.
The results of the internal Chinese deliberations may become clear later this week, when Chinese Premier Wen Jiabao travels to South Korea for a summit with South Korean and Japanese leaders.
China will come under increasing pressure in the region to acknowledge North Korea's role in the Cheonan incident and may be wary of alienating Seoul and Tokyo - two important trading partners.
"While most understand China's dilemma, many see Beijing's 'muddle-through' strategy as a disappointing symbol of its inability to play a leadership role in East Asia commensurate with its rise," wrote Victor Cha, from the Center for International Strategic Studies in Washington, who handled North Korea as a National Security Council official under President George W Bush.