Missile test is first big North Korea challenge for Donald Trump

That North Korea has launched a missile is no longer particularly surprising news.

If this turns out to be a medium-range Rodong missile, as is currently thought, then this is not a startling advance in itself - we've seen numerous such launches before.

What is significant is the timing - this is the first missile test on Donald Trump's watch, while he was hosting the Japanese prime minister no less - and the first real test of how he intends to deal with North Korea's nuclear armed ambitions.

:: Key steps in North Korea's nuclear ambitions

Back in January, Kim Jong-Un said his scientists were in the final stages of being able to test launch an intercontinental ballistic missile, which would represent substantial progress towards his stated goal of a weapons system capable of reaching the US mainland.

"It won't happen!" Mr Trump tweeted in response at the time, but he has yet to lay out any of his thinking as to how he intends to go about stopping it.

For all the President's current focus on the US judiciary and the "peril" from which he says his travel ban would save the American people, his predecessor, Barack Obama, reportedly warned Mr Trump that North Korea would be the biggest threat to national security he will face.

The Obama administration's own policy of "strategic patience" has demonstrably not worked.

Despite increasing sanctions and repeated UN security council resolutions, the Kim regime remains doggedly committed to its weapons programme, which appears to be advancing.

As well as multiple missile launches, North Korea carried out two nuclear tests last year, the second of which was by far its most powerful to date.

Satellite imagery in January suggested the country had restarted the plutonium reactor at its main nuclear site.

Mr Trump's response to this latest launch has been to emphasise his support for Japan, towards which the missile was fired.

"I want everybody to understand, and fully know, that the United States of America is behind Japan, our great ally, 100%," he said.

But that is already where we were - the only reason to doubt the US commitment to its alliance with Japan and South Korea was Mr Trump's own rhetoric on the campaign trail.

Now we appear to be back to the status quo, with the options before Mr Trump as unpalatable as they have been for every US president past, and with the clock now ticking down.

There is little evidence more sanctions and greater economic isolation would stop the regime in the time available, and might just cause it to cling tighter to its warheads, while concessions risk giving the appearance that nuclear blackmail works.

Pre-emptive military action would put 10 million civilians in Seoul in artillery range of the response.

Added to which there is the current political turmoil in South Korea, where the president has been impeached, and the planned US-South Korea missile shield, which China hates and sees as a threat to its security, and North Korea says is pushing the peninsula "to the brink of a nuclear war".

To use the President's vernacular, this is a "yuuge problem, like really, really big," and it's not going to go away of its own accord.