By Adam Brookes
BBC News, Pentagon
US Secretary of Defence Donald Rumsfeld has said he still does not know if North Korea possesses nuclear weapons - despite North Korea's first explicit public assertion that it does have such weapons.
Washington assumes Pyongyang has the materials to make bombs
The hordes of analysts that populate US intelligence agencies, ministries and think tanks will not be running for the fallout shelters just yet.
The fact is, in strategic terms, North Korea's announcement has not really changed much.
Since October 2003, when North Korea said it had reprocessed 8,000 nuclear fuel rods to make plutonium, US intelligence has assumed that North Korea has the materials to make a nuclear bomb - possibly even as many as eight.
But analysts in Washington say that does not mean North Korea's scientists can make a nuclear bomb.
US RHETORIC ON NORTH
19 Jan: Condoleezza Rice refers to North as an "outpost of tyranny"
20 Jan: No mention in George Bush's inauguration speech, though US goal was to "end tyranny in our world"
2 Feb: Mr Bush's State of the Union address says US working with governments in Asia to convince North Korea to abandon nuclear ambitions
Do they have the design or the precision tools or the expertise to turn that plutonium into a warhead?
Do they have a working delivery system for such a weapon - a missile or a bomber? All these things are, apparently, unknown.
At a Nato meeting in Nice, Mr Rumsfeld went out of his way to say he still did not know with any certainty if North Korea possessed a working, deliverable nuclear weapon or not.
"One has to be concerned about it from a proliferation standpoint - if you believe them that they have weapons. I do not know, of certain knowledge, that they do," he said.
Sources with close links to US intelligence agencies say there is a widespread, working assumption among intelligence analysts that North Korea has a nuclear weapons capability.
That assumption will be built on many fragments of information: satellite images which show the nature and duration of activities at the Yongbyon reactor complex, tell-tale chemical signatures in the atmosphere sniffed by American ships and aircraft; signals intercepts, and the testimony of defectors.
The findings of South Korean and other allied intelligence services will also figure in the equation somewhere.
But, as we are so often told, intelligence rarely deals in certainties.
And until North Korea tests a nuclear warhead - or in other words, sets off a nuclear explosion for everyone to see - a measure of uncertainty about what Pyongyang does and does not have will remain.
And Pyongyang's sudden, stark claim to being a nuclear power will not change that.