Rogue states such as Iran face tougher military action from America under Donald Trump, the director of the CIA has warned, as he said the US is “closer now than we have ever been” to the threat of nuclear missiles from North Korea.
Mike Pompeo urged Iran to “take note” that Donald Trump’s missile strikes against the Syrian military were a sign the White House was “prepared to engage in activities that are different from what America has been doing these past few years”.
His comments came as China warned that military conflict over North Korea’s nuclear weapon’s programme could break out “at any moment” as a stand off with the US approached breaking point.
Tension over the rogue state’s arsenal risks reaching an "irreversible and unmanageable stage" as a US aircraft carrier group steamed towards the region amid fears Pyongyang is on the verge of a nuclear weapons test that would trigger US retaliation.
Downing Street said it was monitoring the escalation and called on North Korea to abide by international rules.
It came as the United States had reportedly drawn up plans for a pre-emptive military strike against North Korea should it become convinced the rogue state is about to carry out a nuclear test.
That would be a conventional strike, potentially using Tomahawk cruise missiles, to hit North Korea's nuclear test site, launched from US forces that have been massing in the area.
Kim Jong-un has vowed a "big event" to mark the "Day of the Sun," the 105th anniversary of the birth of the nation's founder, his grandfather Kim Il-sung. There was speculation that event could be North Korea's sixth underground nuclear test.
The US has put two Navy destroyers, capable of firing Tomahawks nearby, with one of them only 300 miles from the nuclear test site, NBC News reported. There are also US Air Force bombers in Guam that could be used to target North Korea.
Earlier this week an aircraft carrier, the USS Carl Vinson, was sent to the area with its strike group, which President Donald Trump called an "armada". The US could also deploy cyber attacks
US special forces, including Navy Seals, Delta Force and Green Berets, are already in South Korea for the annual Foal Eagle military exercise.
Senior defence officials have previously denied reports that Seal Team Six, which killed Osama bin Laden, was there rehearsing for a possible "decapitation strike" against Kim Jong-un.
Any military strike by the US in North Korea could spark an all out attack by the hermit state on south Korea.
US officials indicated any action taken by America would have to be cleared first with its South Korean ally.
Mike Pence, the US Vice President, was due to arrive in South Korea on Sunday on a long-planned 10-day trip to Asia.
Aides to Mr Pence said he would reinforce the US commitment to South Korea and consult with them on the way forward. Meanwhile, Japan’s National Security Council discussed how it would evacuate its 57,000 citizens from South Korea in the event of a crisis.
Yoshihide Suga, the Japanese Chief Cabinet Secretary, said: “We will take all necessary steps to protect our people's lives and assets."
US officials said there was a "new resolve" to deal with North Korea since Mr Trump took office. But they indicated the drawing up of a pre-emptive strike option was intended to send a message to North Korea that the new administration was going to be tougher than the last.
It was the third signal to North Korea, following on from Mr Trump's decision to fire 59 Tomahawks at a Syrian air base, and America dropping the largest conventional bomb ever used in combat in Afghanistan this week.
The Pentagon declined to comment on the circumstances in which it would launch military action against North Korea.
Pentagon spokeswoman Dana White said: "We will not publicly speculate on possible scenarios. Commanders are always considering a full range of options to protect against any contingencies,
"Our commitment to the defence of our allies, including South Korea and Japan, in the face of potential threats, remains steadfast."
North Korea vowed a "merciless" response to any US provocation.
A spokesman for the North Korean Foreign Ministry accused the US of "pushing the situation to the brink of war" and "creating a dangerous situation in which a thermo-nuclear war may break out any moment".
In a statement the North Korean People’s Army said the Trump administration had “entered the path of open threat and blackmail".
It said: "The closer such big targets as nuclear powered aircraft carriers come. the greater would be the effect of merciless strikes."
North Korea said US military bases in South Korea, and South Korea's presidential Blue House, would be "pulverised within a few minutes".
A senior Trump administration official sought to play down the suggestion a pre-emptive strike was being considered, calling that "speculative at best".
Mr Trump was spending the weekend at his Mar-a-Lago club in Florida and was being kept informed of developments.
The Chinese and Russian foreign ministers, Wang Yi and Sergey Lavrov, discussed the situation by phone on Friday, with both countries then urging restraint.
Mr Wang said: "Lately, tensions have risen and one has the feeling that a conflict could break out at any moment. Once a war really happens the result will be nothing but multiple loss. No one can become a winner."
Kremlin spokesman Dmitry Peskov said: "Moscow is watching with great concern the escalation of tensions on the Korean peninsula."
William Perry, defence secretary under President Bill Clinton, said there was danger any US strike could escalate into a nuclear war.
He said: "A strike would either be against the nuclear test sire of launch facility. We have to understand the regime in North Korea, while they are evil, they are not crazy. They are not seeking martyrdom. They are not suicidal. I don't think they are going to launch an unprovoked nuclear attack. It's bluster on their part.
"The danger is we could get into some kind of a military conflict with them and it could escalate into a nuclear war. If they are cornered and their regime is about to collapse then they might use the nuclear weapons."
Richard Bitzinger, a military expert at the S. Rajaratnam School of International Studies in Singapore, said Mr Trump had few options at his disposal, even if Pyongyang carried out a test.
He said: "Shooting down a test missile will be tantamount to an act of war, and so would be attacking a North Korean nuclear site. "The North Koreans are already incredibly paranoid that the US wants to go to war against them. This would only solidify their beliefs and make them even more intransigent. It might even trigger an inadvertent war."
Bonnie Glaser, senior adviser for Asia at the Centre for Strategic and International Studies in Washington, said: "Its my sense that Trump is giving China the time and opportunity to step up pressure on Pyongyang. "The most likely outcome is that the Trump administration ends up disappointed with China's limited response, but it is worth a shot."