US President Donald Trump has boasted that his nuclear button is "much bigger" and "more powerful" than North Korean leader Kim Jong-un's.
Mr Trump's tweet is the latest contribution to an increasingly personalised feud between the nuclear-armed leaders.
Unsurprisingly, Mr Trump's unorthodox words sent social media into a frenzy.
It ended a quick-fire day of tweeting by Mr Trump in which he took credit for a lack of plane crashes, announced awards for "corrupt media" and threatened to pull aid from Palestinians for failing to show "appreciation or respect".
Is the 'playground chatter' in new territory?
Just as President Trump's unorthodox Twitter habits have puzzled observers in the past, the latest tweet is again redefining what is considered a diplomatic or presidential tone.
North Korean Leader Kim Jong Un just stated that the “Nuclear Button is on his desk at all times.” Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!— Donald J. Trump (@realDonaldTrump) January 3, 2018
"I guess the president regards this as a show of strength," said Jim Himes, a Democrat representative from Connecticut and a member of the House Intelligence Committee, on CNN. "But, as everybody who's ever been in a... first grade playground recognises, it's usually the person who's most aggressively pounding their chest that is in fact the weak one on the playground."
Eliot A Cohen, who advised the Republican former Secretary of State Condoleezza Rice, said the latest tweet was childish yet deadly serious.
And activists agreed.
I had to just reassure my teen-age daughter not to panic about nuclear war with North Korea because she read Trump’s tweet. I’m so filled with rage at Donald Trump.— Neera Tanden🖖🏼 (@neeratanden) January 3, 2018
Several argued that Twitter should not allow "calls for nuclear war" to be broadcast on its platform.
However, Mr Trump's supporters have defended him, saying his comments were both factually accurate and showed American strength and resolve.
Press OUR Big Button Trump!!!❤️ Its about time you show North Korea who the USA 🇺🇸 is!!!— LuAnne Ledford (@Trinkets1963) January 3, 2018
Could Donald Trump press the button?
Mr Trump's latest comment states the obvious: a US president has immediate access to the nuclear codes.
However, the real process of launching a nuclear attack does not involve any button-pressing.
After high-level consultations, the president would exchange codes with top military officials. They are printed on a card known as "the biscuit", which he carries wherever he goes.
According to US media, Mr Trump's desk does, however, have a button that orders someone to bring him a Diet Coke.
At least that's what US media reported after seeing said button in action during interviews.
Could North Korea launch attack of its own?
North Korea claims it has nuclear weapons and could strike the US, but while analysts agree that Pyongyang has nuclear weapons, it is not clear whether it has the technology to use them in anger.
Meanwhile, in contrast to the bickering on Twitter, the North has just reopened a telephone hotline to the South.
Was President Trump riled by a Fox News report?
The latest outburst came a day after Mr Kim's speech, to which President Trump initially reacted with caution. "Perhaps that is good news, perhaps not - we will see!", he tweeted.
But his later remark left some social media users questioning if the president had been watching Fox News - which had covered the topic a few minutes before. He is known to be a fan of the channel and often tweets along.