evidence: Biden’s remarks, at a fundraising event in New York, could open him to criticism by political opponents that he is speaking in an inartful way about nuclear war – and at a political fundraiser of all places. But they are paradoxically also a little reassuring because they reveal a president who is deeply conscious of the risks of escalation with the volatile Kremlin leader. And whether they were meant for public consumption or not, his comments will have the effect of signaling to Putin that any use of nuclear arms – even a smaller battlefield device – could create a cascade of consequences that could lead to global disaster. In other words, Biden may be reasserting a measure of deterrence after Putin warned that he was not bluffing over his threat to possibly use a nuclear bomb. [...] US officials have also said, however, that they have detected no sign that Russia is moving or readying any of its tactical nuclear weapons, which can be small enough to target soldier formations or big enough to destroy a city. A US official told CNN’s Jeremy Diamond on Friday that Biden was speaking "frankly" following Putin’s "irresponsible and reckless" rhetoric but that his comments were not based on any new information about Russia’s nuclear posture. There has also been no shift in the US nuclear posture, the official said.