Thomson Reuters
U.S. President Trump pauses as he announces his decision to withdraw from Paris Climate Agreement at White House in Washington
The comment was "all Trump," said another administration official who, like the first, requested anonymity.
At a Tuesday discussion on the opioid crisis, Trump said: "North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen."
U.S. officials and analysts cautioned against engaging in rhetorical shouting matches with Pyongyang, which in turn said it was considering a strategy to fire missiles at the U.S.-held Pacific island of Guam.
The senior administration official who deals with the North Korea issue told Reuters: "President Trump's comment was unplanned and spontaneous."
"There had not been any discussions about escalating the rhetoric in response to North Korean leader Kim (Jong Un)'s statements or about the possible effects of doing that," said the official, who spoke on condition of anonymity.
"Nevertheless, it is important for the North Koreans to understand that this country's strategic patience is exhausted and that our resolve to defend our allies, whatever is required to do that, is not."
Privately two other U.S. officials, who also spoke on condition of anonymity, said the president's threat of "fire and fury" was not helpful and threatened to evoke an undesirable response from the North Korean leader.
Damir Sagolj/Reuters
It also risked alienating U.S. allies Japan and South Korea, as well as adversaries China and Russia, all of whom Washington wants to help pressure Kim to abandon his pursuit of a robust nuclear arsenal capable of striking the continental United States.
On Wednesday, Trump appeared to temper his comments by expressing hope that the U.S. nuclear arsenal would never need to be used.