Donald Trump has said that his “fire and fury” threats against North Korea have not been “tough enough” as he warned Pyongyang risks being “in trouble like few nations have ever been.”

After days of escalating rhetoric between the Trump administration and North Korea over the threat posed by Pyongyang's nuclear and missile programmes, the President showed no signs of toning down his language, even as 60 members of Congress signed a letter protesting his “irresponsible and dangerous” statements.

“It’s about time someone stood up for the people of our country,” the US President told reporters as part of two separate addresses to the media before and after a security briefing with top advisers.

Mr Trump said earlier this week that North Korea faces “retaliation with fire and fury unlike any the world has seen before” if it continues to threaten the US, rattling both allies and adversaries and leading to the letter of complaint from Congress sent to Secretary of State Rex Tilleron on Thursday.

“Frankly, the people who were questioning that statement, was it too tough? Maybe it wasn’t tough enough,” Mr Trump said. “And we’re backed 100 per cent by our military, we’re back by everybody and we’re backed by many other leaders. And I noticed that many senators and others came out today very much in favour of what I said. But if anything that statement may not be tough enough.”

Taking specifically about North Korean leader Kim Jong-un, the President said: “He has disrespected our country greatly. He has said things that are horrific. And with me, he's not getting away with it. He got away with it for a long time between him and his family. ... This is a whole new ball game.“

Mr Trump's latest remarks came after North Korea's state-run media claimed it was formulating plans to strike the US territory of Guam with “historic enveloping fire” and taunted Mr Trump as “bereft of reason” and someone for whom “only absolute force can work.”

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

It is not the first time North Korea has threatened Guam, a small United States territory that hosts a US military outpost. But the North Korean military’s claims via state media that it would have plans to strike Guam with four missiles completed by “mid-August” prompted Mr Trump's latest response. When asked if he was considering a preemptive strike, Mr Trump responded: “We don’t talk about that. I never do.” But he did say that would soon be announcing a plan to invest billions of dollars in missile defence to protect the US.

The President said the US has been negotiating with North Korea for 25 years and that his nation “would always consider negotiations” - but blamed his predecessors for a lack of progress. President Bill Clinton, he said, was “weak and ineffective”, while President Barack Obama “didn’t even want to talk about it,” he added.

“The people of this country should be very comfortable,” Mr Trump said. “And I will tell you this: 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 can be very, very nervous. I’ll tell you why. And they should be very nervous. Because things will happen to them like they never thought possible, OK? He’s been pushing the world around for a long time.”

Mr Trump added that was “not a dare” - perhaps reflecting the fact the US and North Korea had been trading threats - but was instead “a statement of fact.”

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Speaking after Mr Trump, US Defence Secretary James Mattis said that the US military “was ready” to respond to an attack by North Korea but that the US prefers a diplomatic response.

The latest war of words between the US and North Korea was sparked by reports that North Korea had successfully miniaturised a nuclear weapon to place atop a ballistic missile. Tensions had already been raised by two intercontinental ballistic missile (ICBM) tests by Pyongyang in July and NBC News reported on Thursday that multiple US intelligence agencies - including the CIA - now agreed that the North had taken the significant step of miniaturising a weapon.

The rhetoric has left countries in the region uneasy with a number calling for calm. China also rebuked Mr Trump’s role in escalating tensions via a piece in state outlet Xinhua, warning that “such a hostile approach will do little but make things worse.”

“Reality has shown that tough tit-for-tat confrontations can lead nowhere, and that only dialogue can help address reasonable security concerns of the related parties for a solution acceptable to all, ensure denuclearisation on the peninsula and bring a lasting peace to the entire region,” the editorial said.

Mr Trump also said that new sanctions on North Korea approved by the UN Security Council last week that could slash by a third the country's $3 billion annual export revenue probably “will not be as effective as a lot of people think it can be, unfortunately.” Mr Trump praised China and Russia for backing the sanctions, but said that China could be doing more to help the US rein in North Korea, suggesting that if China does so, he may change his views on trade between Americans and the Chinese - a topic which he has constantly said he will do something about.

“We lose hundreds of billions of dollars a year on trade with China,” Mr Trump said, referring to the large US-China trade deficit, which he has repeatedly railed against. “They know how I feel. It’s not going to continue like that. But if China helps us, I feel a lot differently toward trade, a lot differently toward trade.”

Senior Democrats had called the language “reckless” with some of those in Congress arguing that strikes on North Korea would require their sign off. However Republican Senator Lindsey Graham said on Thursday that Mr Trump wouldn't need Congressional approval but urged his colleagues to grant it as a “last resort”.

“It would be very smart if the Congress could come together and tell the president 'you have our authorisation to use military force ... as a last resort.' That would sent a signal to North Korea and China, that would probably do more good to avoid war than anything I could think of,” Mr Graham told conservative radio host Hugh Hewitt. He added that passing a military authorisation for North Korea would require Democrats to “take their hatred of Donald Trump and park it.”

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Mr Graham also backed Mr Trump to back-up his words with action.

“If negotiations fail, he is willing to abandon 'strategic patience' and use pre-emption,” he said. “I think he's there mentally. He has told me this.”

“I'm 100 percent confident that if President Trump had to use military force to deny the North Koreans the capability to strike America with a nuclear-tipped missile, he would do that,” Mr Graham added.

Some officials in the Trump administration have sought a calmer tone, with US Secretary of State Rex Tillerson saying earlier in the week that Mr Trump was engaging in a “pressure campaign” that, along with “engagement of China and Russia,” would deter North Korean aggression.

However, former diplomatic officials have criticised Mr Trump. Susan Rice, who served as national security adviser to Barack Obama, wrote an opinion piece lambasting Mr Trump's “dangerous” path and warning that the president had either indulged in the “folly” of an empty threat or was pondering the “lunacy” of war. Former US President Jimmy Carter also rebuked officials in both nations over their threatening language.