The Times says the US will accept a nuclear North Korea, in the end

Washington Eyes a Cold War Strategy Against North Korea

This summer, the Trump administration declared outright that if Mr. Kim succeeded in reaching that goal, conventional deterrence would not be enough. 

In a series of public statements, Mr. Trump’s national security adviser, Lt. Gen. H.R. McMaster, said that the methods that worked so effectively in the Cold War would not apply in the case of North Korea.

“The North Koreans have shown, through their words and actions, their intention to blackmail the United States into abandoning our South Korean ally, potentially clearing the path for a second Korean War,” General McMaster said, suggesting that the assumption that North Korea wanted a nuclear weapon only to assure survival may be wrong. 

He talked, on several occasions, about how a “preventive war” might be necessary if diplomacy failed.

“The president’s been very clear about it,” he said at another point. 

“He said he’s not going to tolerate North Korea being able to threaten the United States.”

. . . .

But one thing is clear: Whatever threats that Washington and Beijing issued in the past few months — sanctions, and the threat of oil cutoffs — have clearly not deterred Mr. Kim. 

Now he is betting that he can complete his project — solving the last technical details — before the United States, its allies and China can agree upon a unified response.

So far, that bet has proved correct. 

. . . .

Of course, no American official is prepared to admit that the United States is willing, however unhappily, to rely on conventional deterrence and live with a North Korean nuclear missile capability that can reach American shores as well. 

After all, a succession of American presidents, from Bill Clinton to George W. Bush to Barack Obama, have all said that would be intolerable.

But clearly that appears to be where the United States is headed.

Unless, of course, we really are headed for war.

Preventive and non-nuclear, if we start it before Kim is really ready to nuke us.

Or much, much worse, whoever starts it, us or Kim, if it starts after Kim has made himself ready.

Once it is too late for a preventive war the best that can happen, for the US, would be for Kim to successfully bully us out of the peninsula and, over time, force us to accept a "one Korea" policy, as China forced us to evacuate and abandon Taiwan and accept one China.

Or I suppose we could end up fighting a conventional war against NK to defend SK, entirely in the South, as we did to defend South Vietnam, so as to risk neither Chinese intervention on the side of NK nor NK nuking San Francisco.

And then lose, in the end, anyway.

South Korea might have a better chance of winning without us because it would have every incentive to take the risk of invading and trying to crush the North, and far less to lose.