Early this morning on the Korean Peninsula, the launchers were in position… more missiles took to the sky.

Unlike yesterday though, these surface-to-surface weapons were fired by U.S. and South Korean forces. It was partly a military exercise to counter "North Korea's destabilizing and unlawful actions," said a statement from U.S. Forces Korea.

But it was also meant to carry a big message for Pyongyang: the U.S. commitment to South Korea and the region is "ironclad."

At the request of the U.S., South Korea and Japan, the UN Security Council held an emergency meeting Wednesday afternoon.

Trouble is, after yesterday's successful test of what North Korea claims was its first intercontinental ballistic missile, the stakes have never been higher and the options for Washington never so limited.

North Korean leader Kim Jong-un's missile carried a message too.

It was a "package of gifts" to the Yankees on their Independence Day, said the state news agency, to show Pyongyang's ability to "strike the arrogant U.S. face."

North Korean leader Kim Jong-un watches the test-fire of intercontinental ballistic missile Hwasong-14 in this photo released by North Korea's Korean Central News Agency July 4. (KCNA/Reuters)

It also seems to demonstrate Kim Jong-un's ability to strike the U.S. mainland.

For test purposes, the so-called Hwasong-14 missile was fired at a very steep angle, going almost straight up 2,800 kilometres into space before shooting down into the Sea of Japan some 39 minutes later.

Experts say if you flatten out that path, the missile has enough range to hit North America. David Wright, a physicist with the respected Union of Concerned Scientists, estimates the distance at 6,700 kilometres.

"That range would not be enough to reach the lower 48 states … but would allow it to reach all of Alaska," he writes in his blog.

At that rate, it could also hit Whitehorse in Yukon. Other international experts say the potential distance could be more than 9,000 kilometres, which would put San Francisco, as well as Vancouver, at risk.

In January, U.S. President Donald Trump tweeted that North Korea's long-standing threat to hit the U.S. mainland with a nuclear missile "won't happen!"

U.S. Secretary of Defence Jim Mattis: 'It would be a catastrophic war.' (Virginia Mayo/Associated Press)

Suddenly it seems like it really could.

There is no evidence that North Korea has solved the technical challenges of putting a nuclear warhead on its missiles and delivering it accurately, but that now seems just a matter of time.

And it seems there is little the U.S. — or anyone else — can do to keep Pyongyang from becoming a nuclear power.

The U.S. has already done plenty of sabre-rattling. Trump boasted about "sending an armada!" when he sailed big battle groups near North Korea and then flew bombers overhead.

But the military option is complicated and very risky.

It's believed North Korea could already have as many as 20 nuclear weapons, as well as scores of missiles hidden in underground caves around the country. Hitting all of these in a preemptive strike would be almost impossible, and any attempt risks triggering a nuclear war.

Diana speaks to CBC News Asia correspondent Saša Petricic about the challenges of covering North Korea. Watch The Investigators Saturdays at 9:30 pm ET (replays Sundays at 5:30 pm ET) on CBC News Network 2:40

Even without these, Pyongyang could easily hit Seoul with conventional weapons in retaliation, putting 10 million people in the line of fire. Or it could target Japan with missiles that have been proven.

"It would be a catastrophic war," U.S. Defence Secretary James Mattis said on CBS's Face the Nation in May. "A conflict in North Korea would probably be the worst kind of fighting in most people's lifetimes."

The U.S. has reportedly tried other types of warfare, including cyberattacks meant to sabotage North Korea's weapons program, but it hasn't stopped the missiles from getting more sophisticated and more capable.

Gleaming towers

Tough economic sanctions imposed by the UN and the U.S. also seem to have failed.

Indeed, when I was in Pyongyang in April, Kim Jong-un showed off an entire new neighbourhood of gleaming modern towers that North Korea had built and equipped despite outside attempts to cripple his economy.

There seem to be plenty of loopholes in China that allow money and goods to keep flowing.

Washington may have tried to convince Beijing to crack down, and China may have appeared to co-operate by banning imports of North Korean coal. But official Chinese figures show overall trade between the two countries is actually up more than 37 per cent this year.

After yesterday's missile test, Trump made another attempt to convince Beijing to pressure Pyongyang, tweeting: "Perhaps China will put a heavy move on North Korea and end this nonsense once and for all!"

But so far, China seems to be unwilling or unable to force Kim Jong-un to back down, despite sharing frustration over his defiant missile tests.

Doing the opposite

Beijing's main fear isn't an attack by Pyongyang. It's a worry that the U.S. will ramp up its military intervention on China's doorstep. It has already protested loudly about sophisticated radar and anti-missile installations in South Korea.

Not surprisingly, China's leaders continue to press for negotiation between Washington and Pyongyang, urging both sides to scale back their weapons systems.

Instead, both are doing the opposite.

Korea never seemed especially interested in negotiations, even when the two sides were talking in the Bill Clinton and George W. Bush presidencies. It never stopped developing nuclear missiles then.

And from what Kim Jong-un sees as a new position of strength, compromise must seem even less appealing now.