WASHINGTON — Although the Trump administration moved an aircraft carrier strike group toward Korea and warned that it would respond forcefully if North Korea conducts a nuclear test this weekend, likely U.S. military options range from bad to worse.

Satellite imagery has shown preparations at North Korea’s Punggye-ri nuclear weapons site, including more military personnel and mounds of dirt from recent excavations, U.S. officials and outside experts said.

North Korea’s state news media has warned that Kim Jong Un’s government may use today’s national holiday, marking the birthday of the country’s founder, Kim Il Sung, for a weapons test, although it could be another ballistic missile or something less provocative.

The Pentagon has moved the Carl Vinson carrier strike group to waters near the Korean Peninsula as a show of force, and President Donald Trump said Wednesday that submarines were also on the prowl if necessary.

“We have submarines — very powerful, far more powerful than the aircraft carrier. That I can tell you,” Trump said on Fox News. U.S. ballistic missile submarines, known as “boomers,” are designed specifically for stealth and the launching of conventional and nuclear warheads, according to the Navy.

The North Korean military accused the Trump administration Friday of “maniacal military provocations” and threatened to attack U.S. bases in South Korea and other targets “within minutes” if a U.S. attack is launched.

“We will go to war if they choose,” Vice Minister Han Song Ryol said in Pyongyang.

Threats and bluster are part of a familiar and long-running game of brinksmanship between the U.S. and North Korea, but this time it has been made more dangerous by two volatile new players: Kim and Trump.

Kim, the latest member of North Korea’s ruling dynasty, is largely following the path set by his father and grandfather. He has redoubled efforts to build a nuclear arsenal, but U.S. analysts don’t believe he will launch a suicidal attack that would bring about the end of his regime.

“The most unpredictable part of this story is Trump, not North Korea,” said Sue Mi Terry, a former CIA analyst who focuses on the country. “North Korea is doing what it always does.”

In recent weeks, Trump has challenged U.S. foreign policy orthodoxy with headline-grabbing displays of military might and head-spinning reversals in policy.

Last week Trump approved firing 59 cruise missiles at a Syrian airfield that the White House said had been used to launch a poison gas attack on a rebel-held village. It was the first intentional U.S. attack on a Syrian government site in the six-year civil war.

And Thursday, the Air Force dropped its most powerful conventional bomb, an 11-ton weapon, on a cave-and-tunnel complex that it said Islamic State fighters were using in eastern Afghanistan.

It was the first time the Massive Ordnance Air Blast had been detonated in combat.

The explosion killed 36 militants, Afghan officials said Friday.

Asked Thursday if use of the huge bomb was meant as a warning to North Korea, Trump gave an ambiguous answer.

“I don’t know if this sends a message. It doesn’t make any difference if it does or not,” he said. “North Korea is a problem. The problem will be taken care of.”

The problem has bedeviled the past three presidents.

Diplomatic accords meant to stop or slow North Korea’s nuclear development all faltered, and recent tests show the country is fast closing in on the capability to build a ballistic missile that could reach U.S. territory in the Pacific or beyond.

Defense Secretary James N. Mattis sought twice this week to play down the possibility of a U.S. attack and the significance of the carrier strike group, noting that U.S. warships regularly operate in the western Pacific.

On Thursday, however, he offered tougher talk. “The bottom line is North Korea has got to change its behavior,” he said.

The State Department spokesman, Mark Toner, warned of “an urgency to the situation.”

“Provocations from North Korea have grown, frankly, too common, too dangerous to ignore anymore,” Toner said.

Trump called Chinese President Xi Jinping this week to enlist his support in resolving the crisis, days after the two leaders conferred at Mar-a-Lago in Florida.

An influential Chinese newspaper, the Global Times, subsequently called for “severe restrictive measures that have never been seen before, such as restricting oil imports to the North” if Pyongyang engages in further provocative activity.

U.S. analysts say a full oil embargo could paralyze North Korea in months, but Beijing is unlikely to enforce it because of fear it would send millions flooding across its border and destabilize its Communist ally and neighbor.

Chinese Foreign Minister Wang Yi warned Friday of “storm clouds” gathering, saying “tit-for-tat threats between the United States and North Korea with daggers drawn has created a dangerous situation worthy of our vigilance.”

It’s unclear how Trump might respond to a nuclear test.

One option that might fit his recent pattern — symbolic but dramatic — would be to reintroduce U.S. nuclear weapons in South Korea. President George H.W. Bush removed them in 1991, and U.S. policy since has been to seek “de-nuclearization” of the Korean Peninsula.

A major U.S. attack against North Korea could involve firing conventional cruise missiles from warships, attack submarines and warplanes against air defense sites, missile batteries, submarine pens and other targets. It could pull in South Korean and Japanese forces plus dozens of U.S. fighter jets and heavy bombers stationed on Guam.

Under the War Powers Act, passed by Congress during the Vietnam War, presidents can order U.S. forces into combat without congressional approval, but only for limited periods and only in response to an attack on the U.S. or its military.

But every White House since the law was passed in 1973 has taken the position that it is an unconstitutional limit on the president’s power as commander in chief. In the most recent case, for example, Trump did not seek congressional approval before he ordered the missile strike in Syria.

A more limited military strike on Punggye-ri and other nuclear sites could risk releasing radiation. Much of the infrastructure is supposedly buried deep underground anyway.

Cyberattacks against military command and control facilities are possible, but much of the agrarian country is off the internet. The Obama administration reportedly launched cyberattacks against North Korea’s missile program, but the effects were difficult to discern.

U.S. warships or Japanese anti-missile systems could try to destroy a North Korean missile over the ocean, while a new anti-missile battery in South Korea could target one closer to its launch. But a miss could be more of an embarrassment than a deterrent.

Diplomatic options are equally problematic. North Korea has ignored or defied numerous United Nations resolutions intended to restrain its nuclear and missile programs.