"My first order as President was to renovate and modernize our nuclear arsenal. It is now far stronger and more powerful than ever before," Trump wrote just before 8 a.m. ET from his golf resort here. "Hopefully we will never have to use this power, but there will never be a time that we are not the most powerful nation in the world!"
Trump was apparently referring to a review of US
nuclear weapons that began earlier this year, which he directed Defense Secretary James Mattis to undertake in a presidential memorandum signed during a January visit to the Pentagon.
Such reviews of the US nuclear posture are required by Congress and typically occur every eight years. The Pentagon last conducted a review in 2010 that was ordered by then-President Barack Obama.
It is unclear to what extent, if any, the US nuclear arsenal has been modernized since Trump took office. Such efforts would require billions of dollars allocated by Congress, and Trump's administration has proposed increasing spending on nuclear programs by 11%, more than the overall increase to the defense budget.
Significant changes to the US nuclear arsenal capability would be heavily governed by existing treaties with other nuclear states. The longstanding goal of those agreements has been to reduce the overall number of nuclear weapons worldwide.
Trump's morning statement came amid bipartisan concern over Trump's scaled-up rhetoric about North Korea, which came to a head Tuesday afternoon.
"North Korea best not make any more threats to the United States," Trump said from the clubhouse of his resort. "They will be met with fire and fury like the world has never seen. He has been very threatening beyond a normal state and as I said they will be met with fire and fury and frankly power the likes of which this world has never seen before."
The White House initially declined to clarify Trump's remarks, saying they spoke for themselves. Aides would not name who Trump consulted before delivering the comments.
On Wednesday morning, a White House spokeswoman said Trump had been in touch with national security officials before he delivered his statement.
"The President and chief of staff Kelly are, and have been, in constant contact with members of the NSC team," said the spokeswoman, Lindsay Walters.
While he delivered his remarks, Trump appeared to be reading from a piece of paper, but a person familiar with the comments said Trump wasn't reading from a prepared script. The papers were related to the opioid meeting that Trump was convening at his golf club.
The warning was improvised in the moment, and not part of a scripted statement, according to three people with knowledge of the remarks.
"General Kelly and others on the NSC team were well aware of the tone of the statement of the president prior to delivery," White House press secretary Sarah Huckabee Sanders said. "The words were his own. The tone and strength of the message were discussed beforehand."
Trump's secretary of state Rex Tillerson told reporters Wednesday that Trump was aiming to use language that Kim Jong Un would understand.
"I think what the President was doing was sending a strong message to North Korea in language that Kim Jong Un would understand because he doesn't seem to understand diplomatic language," Tillerson told reporters aboard his aircraft, which was traveling back from a summit meeting in Malaysia.
But Tillerson also sought to cool fears of imminent war with North Korea.
"I have nothing that I have seen and nothing that I know of would indicate that the situation has dramatically changed in the last 24 hours," he said.