A senior Trump administration official denied reports the US was prepared to launch a preemptive conventional weapons strike against North Korea if it appeared the regime was ready to launch a nuclear weapons test, according to Reuters.
The US fears North Korea will perform the nuclear test to coincide with the national 'Day of the Sun' on Saturday commemorating the anniversary of its founding president Kim Il Sung.
US intelligence officials told NBC if the US is convinced North Korea will follow through on a test, it can preemptively deploy Tomahawk missiles from two warships parked in the region.
Bombers are also being lined up in Guam, and cyber and special operations on the ground may be utilised, the officials said.
But a member of the administration shot down the idea, describing the report as "flat wrong", while another official told Reuters it was "speculative at best".
The Pentagon declined comment, saying, as a policy, it does not discuss future operations "nor publicly speculate on possible scenarios."
CIA director Mike Pompeo said North Korea was closer now than it had ever been to being able to threaten the United States with a nuclear-tipped intercontinental missile and increased its technical know-how with each new test.
This in turn reduced U.S. options and "makes it more likely that you get a bad decision, a tough day for the leader of North Korea," he told Washington's Center for Strategic and International studies.
Aerial photos taken Tuesday show continued activity at the Punggye-ri Nuclear site where US officials fear a nuclear device has been installed in a tunnel ahead of another test.
Tensions remain high after President Donald Trump sent the USS Carl Vinson aircraft carrier strike group to the Korean Peninsula.
On Thursday, North Korea said it would launch a "merciless retaliatory strike" against US military action after issuing another warning the day before.
While a "big event" slated for Thursday turned out to be the unveiling of new skyscrapers in Pyongyang, US officials told NBC a nuclear test could come as early as this weekend.
Washington said North Korea should see the strikes as a sign of U.S. resolve, but U.S. officials have played down the prospect of any military strike against North Korea, which would likely provoke massive North Korean retaliation and huge casualties in Japan and South Korea and among U.S. forces in both countries.
China, North Korea's sole major ally and neighbor, opposes its weapons program and has called for talks leading to a peaceful resolution and the denuclearization of the peninsula.
"Military force cannot resolve the issue," Chinese Foreign Minister Wang Yi told reporters in Beijing. "Amid tensions we will also find a kind of opportunity to return to talks."
Japanese Prime Minister Shinzo Abe also underscored fears about possible threats from North Korea, telling parliament in Tokyo that Pyongyang could have the capacity to deliver missiles equipped with sarin nerve gas.
Kim Jong-un made a public appearance in Pyongyang on Thursday, to open a housing project featuring residential tower blocks of various shapes - round, square and octagonal - with the tallest proclaimed as 70 storeys, or 234 metres, high, and including nearly 5,000 apartments in total.
Around 200 foreign journalists are in Pyongyang as the country marks the 105th anniversary of 'Day of the Sun'.
Officials had given no details as to the nature of a planned "big" event today or where it would take place, and similar announcements in the past have been linked to relatively low-key set pieces. In the end, it turned out to be the grand unveiling of a block of flats.
In 2016, for example, foreign journalists underwent hours of investigation by North Korean officials ahead of what turned out to be a pop concert to mark the finale of a ruling Workers' Party congress.
Washington-based 38 North, who monitors North Korea, has reported "unusually high levels of activity" at the Punggye-ri Nuclear Test Site over the past four weeks.
New satellite imagery from April 2 showed there was more activity around the North Portal, which is the tunnel where the four most recent nuclear tests have taken place.
Today it was revealed that Kim Jong-Un had overseen a special forces commando operation, watching from an observation post as special forces dropped from light transport planes "like hail" and "mercilessly blew up enemy targets".
With a broad smile on his face, Kim praised his troops for their precision, saying "the bullets seemed to have their own eyes", KCNA said, without identifying when the operation was held.
The Rodong Sinmun - the official mouthpiece of the ruling Workers' Party - carried several photos from the contest including one of Kim watching the troops parachuting down from jets into an open field. Another showed him grinning from ear-to-ear as he walked by cheering soldiers.
"The contest proved once again that our Korean People's Army... will show a real taste of gun shot and real taste of war to the reckless invaders," KCNA said.
It came as Japan warned North Korea may have the capacity to deliver missiles equipped with sarin nerve gas.
Prime Minister Shinzo Abe said: "There is a possibility that North Korea already has a capability to deliver missiles with sarin as warheads."
South Korea said today it believed it would be consulted by the United States before any possible pre-emptive U.S. strike against Pyongyang.
China urged the North to halt its nuclear programme in exchange for greater protection from Beijing.
An influential state-backed Chinese newspaper said the best option for North Korea and its leader Kim Jong Un was to give up its nuclear ambitions.
"As soon as North Korea complies with China's declared advice and suspends nuclear activities ... China will actively work to protect the security of a denuclearised North Korean nation and regime," said an editorial in the Global Times, which is published by the Communist party's People's Daily.
Yesterday, Chinese President Xi Jinping called for a peaceful resolution to the North Korean problem in a telephone conversation with President Trump on Wednesday.
Trump tweeted that he had "a very good call" with Chinese leader Xi Jinping Tuesday night dealing with 'the menace of North Korea.'
He promised Xi on Tuesday that they would get "far better" trade terms with the U.S. if they managed to de-fang the hostile North Korean regime.
But in the same digital breath - on Twitter - he pledged to handle Pyongyang with or without Beijing's help.
"I explained to the President of China that a trade deal with the U.S. will be far better for them if they solve the North Korean problem!" Trump tweeted Tuesday.
And today, he tweeted that he had "great confidence that China will properly deal with North Korea."
The president is increasingly concerned with the threat of a nuclear program being developed by North Korean dictator Kim Jong-un.
"North Korea is looking for trouble. If China decides to help, that would be great. If not, we will solve the problem without them! U.S.A." Trump continued Tuesday.
Pyongyang rattled a saber in Washington's direction on Monday, saying it would mount a defense against "reckless acts of aggression" after the Trump administration sent an aircraft carrier strike group toward the Korean peninsula.
The strike group consists of the USS Carl Vinson, a missile carrier and two destroyers.
The state-run Korean Central News Agency said the North Korean foreign ministry criticized Trump's "reckless acts of aggression" and said American aggression has "reached a serious phase."
Pyongyang "is ready to react to any mode of war desired by the U.S.," the ministry insisted.
In April, 2012, North Korea attempted to launch a long-range rocket ahead of the 100th Day of the Sun. State media later confirmed the launch had failed.
On Wednesday, North Korean officials told foreign journalists in Pyongyang invited to mark the national holiday that their schedule had been canceled, and to instead meet early on Thursday to prepare for a "big and important event".
Visits by foreign journalists to North Korea are rare and tightly coordinated, and security checks at events attended by leader Kim Jong Un are especially rigorous.
North Korea often uses such visits to showcase new construction projects. In recent weeks workers have been putting the finishing touches to the skyscraper-lined 'Ryomyong' street in central Pyongyang.
Kim has made frequent visits to the street to inspect construction work there, according to state media. North Korea has in the past marked its April 15 holiday with tightly choreographed military parades.