When Defence Secretary Leon Panetta visited U.S. troops in South Korea in October and told them that they were on the front line, it was clearly a rhetorical flourish meant to show appreciation for the 28,500 American forces theoretically in firing range of the North.
But less than two months later, North Korean leader Kim Jong-il's death has raised the possibility of true instability on the Korean peninsula. And rather than speaking with colourful bravado, U.S. officials have been at pains to avoid doing or saying anything that could escalate tensions or create the perception of looming conflict.
Indeed, Secretary of State Hillary Clinton on Monday went so far as openly rooting for a smooth handover of power as Kim's son, the untested Kim Jong-un, prepares to take over.
The United States has an interest in a peaceful and stable transition in North Korea, she said.
We are deeply concerned with the well-being of the North Korean people and our thoughts and prayers are with them during these difficult times, Clinton said in a statement late on Monday.
It is our hope that the new leadership of the DPRK will choose to guide their nation onto the path of peace by honouring North Korea's commitments, improving relations with its neighbours, and respecting the rights of its people.
Expect more messages like that in the coming days, and no overtly muscular moves by the Obama administration toward the reclusive state which has twice tested nuclear devices.
The goal is not to create chop in the water, to allow the transition to occur, one U.S. official told Reuters, speaking on condition of anonymity.
A smooth transition that allows a third generation of North Korea's ruling dynasty to take power appears to be the least bad of many undesirable options for Washington, one that leaves hope for further diplomatic engagement over the country's nuclear program.
Other options include terrifying scenarios like collapse of the North Korean state, which could flood neighbouring China and South Korea with refugees and send economic ripples across Northeast Asia.
Alternatively, a power struggle within North Korea's military and political elites would heighten the risk of conflict between North Korea and South Korea, Asia's fourth largest economy, that could drag in the United States.
U.S. IN THE DARK
Despite the high stakes, Washington is largely on the sidelines when it comes to political developments within the North Korean state, where it has no embassy, limited contacts and few insights into the inner circles of power.
That is one reason analysts believe it is important for Washington to work with China, the North's closest ally, which on Monday expressed confidence North Korea would remain united.
The U.S. military, for its part, appears to be taking a wait-and-see approach that reflects caution at an uncertain moment for security on the peninsula.
U.S. officials said American forces in South Korea - who have been preparing for potential conflict since the Korean War ended in 1953 - were so far not put on a higher state of alert following Kim's weekend death.
That decision was a departure from the one taken by the South Korean and Japanese militaries, which did raise their alert levels.
U.S. officials also appeared to play down concerns about a North Korean missile test shortly before the announcement of Kim's death, saying it was likely pre-scheduled - and not a symptom of escalating tensions.
We have not seen any change in North Korean behaviour of a nature that would alarm us, General Martin Dempsey, chairman of the U.S. military's Joint Chiefs of Staff, said during a trip to Germany, according to Defence Department media.
There is uncertainty about how much support the third generation of the North's ruling dynasty has among the country's elite, especially in the military, and concern the young Kim might need a military show of strength to help establish his credentials.
U.S. and South Korean officials have cited the North's succession politics as a reason behind deadly provocations in 2010, when the North was blamed for sinking a South Korean warship and launching an unprovoked shelling of a South Korean island.
U.S. officials who spoke with Reuters declined to speculate about whether more provocations were likely.
Trying to predict what the North will do now is a fool's errand, said one U.S. military official, speaking on condition of anonymity.
Dempsey noted that the younger Kim was untested - reinforcing the idea that a wild-card ruler was about to take the helm of a country that already been something of a black-box to American intelligence officials.
We will have to see ... how he reacts to the burden of governance that he hasn't had to deal with before, Dempsey was quoted as saying.
Another scenario, one that seems distant and would not necessarily please China, is the peaceful reunification of the two Koreas.
Even that has downsides: South Korea has studied in intimate detail the reunification of East and West Germany and knows the heavy financial and social costs it would bear to bring impoverished North Korea up to the South's living standards.
For now, the Obama administration is signalling it remains open to engagement with North Korea, while saying the country must take steps toward denuclearization for that to occur.
A U.S. congressional aide said that although the odds of the North responding positively to the offer were slim to nil, it was still the right move diplomatically.
It signals a lack of hostile intent. It (also) puts a question to the North Korean leadership, to the new leadership, early in its formation, the aide said.
It says: we have this unresolved relationship that sits in front of us. We need to give them an answer, what are we going to do about the American-(South Korean) offer?
(Additional reporting by Andrew Quinn, Arshad Mohammed and Paul Eckert; editing by Mohammad Zargham and Philip Barbara)