Video: Mr Trump made the comments before a security briefing at Trump National Golf Club in New Jersey. (Photo: AP/Evan Vucci) (ABC News)
Related Story: North Korea threatens to hit Guam after Trump issues 'fire and fury' warning to Kim Jong-un
President Donald Trump has ratcheted up his rhetoric toward North Korea, saying it should be "very, very nervous" if it even thinks about attacking the United States or its allies.His comments came after Pyongyang said it was making plans to fire missiles over Japan to land near the US Pacific territory of Guam.
- Donald Trump says Kim Jong-un has been pushing world around for a long time and North Korea better get its act together
- North Korea says it's planning a strike near Guam
- Mr Trump has been meeting with national security advisers
"The people of our country are safe. Our allies are safe. And I will tell you this: North Korea better get their act together or they're going to be in trouble like few nations ever have been in trouble in this world," Mr Trump told reporters in New Jersey.
Far from toning down his words after saying on Tuesday that any threats by Pyongyang would be "met with fire and fury like the world has never seen", Mr Trump said those remarks may have not gone far enough.
"Maybe it wasn't tough enough. They've been doing this to our country for a long time, for many years," Mr Trump added.
"And it's about time that somebody stuck up for the people of this country and for the people of other countries."
US Secretary of State Rex Tillerson, who was in Guam this week on a previously scheduled visit, had earlier played down Mr Trump's "fire and fury" warning, saying he did not believe there was an imminent threat from North Korea and "Americans should sleep well at night".
But when Mr Trump was asked if he would consider a pre-emptive strike against North Korea to deny it the ability to launch a nuclear attack against the United States, he said: "We'll see what happens."
"If North Korea does anything in terms of even thinking about attack of anybody that we love or we represent or our allies or us, they should be very, very nervous," he said.
"I'll tell you what. And they should be very nervous. Because things will happen to them like they never thought possible."Mr Trump praised China and Russia for backing new UN sanctions on North Korea, but pressed Beijing to do more.
"I think China can do a lot more, yes … and I think China will do a lot more," he said.
The United Nations said secretary-general Antonio Guterres was "troubled" by the escalating rhetoric from both sides in the dispute.
"[Mr Guterres] welcomes all initiatives that will help de-escalate the tensions and a return to diplomacy," UN spokesman Stephane Dujarric said.
North Korea's Guam strike plans due mid-August
North Korea's army will complete the plans in mid-August to fire four intermediate-range missiles over Japan to land near Guam, when they will be ready for leader Kim Jong-un's order, state-run KCNA news agency said, citing General Kim Rak Gyom, commander of the Strategic Force of the Korean People's Army.
The plans called for the missiles to land in the sea 30-40 kilometres from Guam.
Such a launch would almost compel the United States to attempt an intercept and possibly generate further escalation.
"Sound dialogue is not possible with such a guy bereft of reason and only absolute force can work on him," North Korea's state-run KCNA news agency said of Mr Trump on Thursday, calling his "fire and fury" comment "a load of nonsense".
Mr Trump's latest warning came after meeting with national security advisers at the golf resort where he is vacationing.
He said the US "of course" would always consider negotiations with North Korea, but added that talks with the North have failed for the last 25 years.
On Mr Kim, Mr Trump added: "He's been pushing the world around for a long time."
Japan's Defence Minister Itsunori Onodera told Parliament a missile attack on Guam would be a Japanese national emergency because it would threaten Japan's existence as a nation.
North Korea's Hwasong-12, which was revealed for the first time at a military parade in April, is an intermediate-range ballistic missile that is believed to have a radius of more than 3,700 kilometres.
It can be fired from mobile launchers, making it hard to detect and destroy on the ground.
By launching a salvo of four, the North would be attempting to make it harder for the US to intercept all of the incoming missiles.
If Pyongyang carries out its threatened show of force and launches missiles toward Guam, it would represent an unprecedented milestone in the already fraught relations between the United States and North Korea.