Washington’s claim that an American spy plane had to take evasive action during an encounter with a Chinese fighter jet off the Korean Peninsula has underlined the extremely tense situation as the US continues to threaten military action against North Korea.

The incident last Sunday involved a US Navy EP-3 reconnaissance aircraft and two Chinese J-10 fighters. Pentagon spokesman Captain Jeff Davis claimed that one of the Chinese fighters slowed, flew below the American plane and then emerged about 100 metres in front of it—a manoeuvre he branded as “unsafe”

Davis declared that the EP-3 was on “a routine mission” in international airspace. What the Pentagon regards as “routine,” however, is sending reconnaissance aircraft and ships to gather electronic and other intelligence on both China and North Korea.

According to Reuters, the spy plane was flying in the East China Sea just 80 nautical miles (150 kilometres) from the Chinese city of Qingdao, the home base for China’s North Fleet. Qingdao also sits opposite the Korean Peninsula. The Pentagon has, of course, not disclosed the nature of the EP-3 mission.

The Chinese defence ministry rejected the Pentagon’s claims and reiterated its opposition to US spy missions off the Chinese mainland. Spokesman Ren Guoqiang declared that the actions of the Chinese pilots had been “legal, necessary and professional.”

He called for an end to US spy missions, saying they “threatened China’s national security, harmed China-US sea-air military safety, endangered the safety of pilots from the two sides and were the root cause of China-US sea-air unexpected incidents.”

The EP-3 reconnaissance operation took place amid continued speculation in Washington that North Korea could be on the brink of testing another long-range missile, or possibly conducting another nuclear test. An American official told the AFP news agency that the test could go ahead as early as July 27 and would either be an intermediate range missile or the type of long-range missile launched on July 4.

That test of what the Pyongyang regime claimed was an intercontinental ballistic missile (ICBM) triggered denunciations by Washington, an emergency session of the UN Security Council and US demands that China take tougher action against North Korea to force it to abandon its nuclear and missile programs.

The Washington Post reported yesterday that in the wake of the July 4 missile test, the Pentagon’s Defence Intelligence Agency (DIA) has revised its assessment of North Korea’s capabilities, claiming that it could have a “reliable, nuclear-capable ICBM” as soon as next year—two years earlier than previously estimated.

The article noted that one of the remaining technical hurdles facing North Korea was the ability of a ballistic missile to re-enter the Earth’s atmosphere without damage to its warhead as a result of intense heat. A US official claimed that North Korea was making final preparations for testing a new re-entry vehicle. “They’re on track to do that, essentially this week,” the official told the Post.

The revised DIA estimate heightens the danger of a US attack on North Korea. The Trump administration has repeatedly declared that it will employ all options, including military force, to prevent North Korea from building a nuclear ICBM capable of hitting the US mainland. Further tests could provide the US with the pretext for launching military strikes.

Speaking at the Aspen Security Forum last weekend, Joint Chiefs of Staff chairman, General Joseph Dunford dismissed claims that the use of military force against North Korea was “unimaginable” due to the devastation another Korean war could cause. Such a war would be “horrific” and would result in “a loss of life unlike any we have experienced in our lifetimes,” he said, but it is not unimaginable.

“What’s unimaginable to me is allowing a capability that would allow a nuclear weapon to land in Denver, Colorado. That’s unimaginable to me. So my job will be to develop military options to make sure that doesn’t happen,” Dunford said.

The Pentagon’s top general also made clear that time was running out for diplomatic efforts and tough sanctions to force the Pyongyang regime to change course. When it was suggested that the North Korean regime would never give up its nuclear weapons, Dunford declared that Secretary of State Rex Tillerson’s diplomacy might not succeed and “there may have to be a follow-up option, which is the military option.”

Dunford supported “an effort to have a concerted economic and diplomatic plan that does cause [North Korean leader] Kim Jong-un to come to the table” to negotiate, but then pointedly added that it made “all the sense in the world … to work this for a few more months.”

In a separate Aspen session, CIA director Mike Pompeo suggested that the US was actively considering plans to assassinate Kim Jong-un and other top North Korean leaders. He told the audience that the problem was not so much Pyongyang’s nuclear weapons, but “the character who holds control over them.” He said he was “confident that the intelligence community will present … a wide range of options for the president” to “separate those two”—that is, the nuclear weapons from the “someone who might well have intent” to use them.

The threat of war on the Korean Peninsula is aimed not just against North Korea but is being used as a justification for a US military build-up throughout the Asia Pacific directed against China. Beijing is not only under intense pressure from Washington to bully Pyongyang into submission, but confronts the danger of a war on its doorstep to oust a regime that has been a long-time ally and buffer against the US and its allies.

A lengthy article in the Wall Street Journal on Monday detailed Chinese military preparations along its northern border with North Korea. Based on a review of Chinese government and military web sites by US analysts, the article stated: “Recent Chinese measures include establishing a new border defence brigade, 24-hour video surveillance of the mountainous frontier backed by aerial drones, and bunkers to protect against nuclear and chemical blasts.”

It cited an article by a retired Chinese major general, Wang Haiyun, who suggested that China had “drawn a red line” for the US: if it attacked North Korea without Chinese approval, Beijing would have to intervene militarily. The Wall Street Journal suggested that the Chinese military was already preparing for such an eventuality, writing: “Beijing appears to be enhancing its capability to seize North Korean nuclear sites and occupy a swathe of the country’s northern territory if the US or South Korean forces start to advance toward the Chinese border.”

While the Wall Street Journal may well be hyping the Chinese threat for its own political purpose, the Chinese military preparations do underscore the risk of a war on the Korean Peninsula turning into a far wider conflict between major, nuclear-armed powers. In this tense and volatile situation that the Trump administration has recklessly placed on a hair trigger, the danger is that any incident—including an accidental mid-air collision between Chinese and US aircraft—can set off events that no-one can control.