With North Korea thumbing its nose at the response to the sinking of a warship, the United States is left wondering how long to keep up its policy of studied coolness toward the communist state.

The UN Security Council last week condemned the sinking of South Korea's Cheonan vessel, which killed 46 people. But it stopped short of blaming North Korea, which claimed a diplomatic victory and demanded Thursday that the United States prove Pyongyang's involvement in the March incident.

The United States has responded to the Korean peninsula's deadliest incident in decades by standing firmly behind South Korea. Secretary of State Hillary Clinton and Secretary of Defense Robert Gates are expected next week in Seoul to announce joint naval exercises, despite objections by China.

But the longer-term US policy toward the North is less clear. Before the Cheonan's sinking, Clinton described a US stance of "strategic patience" -- waiting for Pyongyang to come forward rather than hastily offering incentives.

"How to move forward, and when, are all questions that lots of people are thinking about," said Bonnie Glaser, a senior fellow at the Center for Strategic and International Studies, a Washington think-tank.

"There's a recognition that, based on past patterns and practice, the longer there is a lack of dialogue and interaction, the greater the likelihood for North Korean brinkmanship and provocative action," Glaser said.

"But there's also the risk of getting back prematurely and sending a signal to North Korea that provocative action leads us to re-engage with them," she said.

North Korea has offered to return to six-nation disarmament talks -- which involve China, Japan, the two Koreas, Russia and the United States. It had stormed out last year before carrying out its second nuclear test.

The United States ruled out talks in the wake of the Cheonan sinking. It has since said that North Korea must respect a six-way deal in which it agreed to give up its nuclear program in return for security guarantees and aid.

Kurt Campbell, the assistant secretary of state for East Asian affairs, said Thursday that the United States was willing to sit down with North Korea "under the right circumstances" but did not want to "talk for talking's sake."

Some North Korea watchers say that the United States needs to be more forward-looking and find ways to reach out to ordinary people in the isolated nation.

"There seems to be no exit strategy beyond measures taken in response to the Cheonan incident," said Karin J. Lee, executive director of the National Committee on North Korea, which supports US engagement with Pyongyang.

She said that the United States and South Korea set "very high expectations" for UN Security Council action, even though veto-wielding China had consistently shown reluctance to pressure North Korea over the Cheonan.

"The problem with setting the bar so high that it can't be reached is then the public is disappointed with the outcome," she said.

China is the main diplomatic and political backer of North Korea. It is widely seen as supportive of the status quo, fearing that a collapse of Kim Jong-Il's regime could trigger a flood of refugees and bring a US-allied unified Korea to its doorstep.

Bruce Klingner, a senior research fellow at the conservative Heritage Foundation, said the United States should step up military cooperation with South Korea and -- despite Chinese objections -- carry out the exercises near where the Cheonan sank in the Yellow Sea.

"Given the UN's failure to respond effectively to North Korean aggression, the rest of the world, led by the US and South Korea, must now take the initiative," Klingner said.

"Failure to do so will only embolden Pyongyang and its Chinese enablers," he said.

earlier related report
Clinton, Gates visit Seoul amid tension with North Korea
Washington (AFP) July 18, 2010 - US Secretary of State Hillary Clinton and Defense Secretary Robert Gates visit Seoul Wednesday in a show of solidarity amid fresh tensions with North Korea over the sinking of South Korean warship.

Clinton and Gates are expected to announce joint naval exercises at the meeting with their respective counterparts Yu Myung-hwan and Kim Tae-young on July 21, as Seoul commemorates the 60th anniversary of the start of the Korean War.

Tensions from the three-year conflict, from 1950-1953, remain, with the fallout from a March torpedo attack on South Korea's Cheonan vessel contributing to a tense environment.

A multinational investigation blamed the attack, which killed 46, on North Korea. But the UN Security Council chose not to pin the act on Pyongyang when it condemned the incident last week.

The United States responded to the Korean peninsula's deadliest incident in decades by standing firmly behind Seoul, and is dispatching Clinton and Gates to announce war games over the strong objections of North Korean ally China.

The naval and air drills in the Sea of Japan and the Yellow Sea are about "sending a message" to Pyongyang, and will be "a show of force to the North Koreans... (sending) a very strong message of deterrence," said Pentagon spokesman Geoff Morrell this week in announcing the high-level visit.

A senior US defense official said the exercises would last "over a period of months."

The official, who asked not to be named, also revealed that "anti-submarine warfare capabilities" was a key component of the drills, after a probe of the Cheonan attack identified the involvement of a submarine.

The Pentagon has said China need not be alarmed, with Morrell insisting "no one has any exclusive rights to the Yellow Sea's international waters" and adding Beijing would be notified "when and where" the drills occur.

On the diplomatic front, the trip will be a chance for the United States to coordinate with Seoul on the possible resumption of dialogue with the Communist North.

North Korea has offered to return to the six-nation disarmament talks -- which involve China, Japan, the two Koreas, Russia and the United States -- after last storming out last year before carrying out its second nuclear test.

The United States ruled out talks in the wake of the Cheonan sinking but has since said that North Korea must respect a six-way deal in which it agreed to give up its nuclear program in return for security guarantees and aid.

"The United States and South Korea have always maintained, and our position is clear, that we are prepared under the right circumstances to sit down in a dialogue with North Korea," said Kurt Campbell, assistant secretary of state for East Asia.

But he warned North Korea would have to demonstrate a commitment to change its policies before US and South Korean negotiators would start a dialogue.

"We do not want to talk for talking sake. There has to be a clear determination that North Korea rejects its provocative ways and embraces a path towards denuclearization of the Korean peninsula," he said this week.

On Thursday, a US and a North Korean colonel held landmark 90-minute talks at the border village of Panmunjom aimed at preparing for discussions at level of generals on the Cheonan's sinking.

KCNA, the official North Korean news agency, said agreement was reached on the date, venue and make-up of the delegations for follow-up talks, without giving further details.

The six-party dialogue that began in 2003 aims to persuade Pyongyang to abandon its atomic program, but talks could also touch on the recent extension of Washington's wartime command of South Korean forces until 2015, announced in June in a demonstration of the strength of the alliance.

US President Barack Obama and South Korean leader Lee Myung-Bak in late June extended the long-standing agreement -- given a five-year shelf life in a 2007 agreement -- which would see the United States assume operational command of South Korean forces if war broke out on the Korean peninsula

Some 28,000 US troops are stationed in South Korea to support 670,000 South Korean soldiers, who face North Korea's 1.2-million strong army.