Among the many challenges facing the next occupant of the White House, few will be more pressing, or more complex, than that posed by North Korea's seemingly inexorable drive to nuclear statehood.

As adamant as Washington is about never accepting the North as a nuclear weapons state, the ground reality is of a country rapidly closing in on its strategic goal of possessing a direct and credible nuclear strike threat against the US mainland.

Pyongyang's weapons programme has accelerated sharply in this US election year, with two nuclear tests and around 25 missile tests in defiance of multiple UN resolutions and sanctions.

"Every single day that goes by, North Korea becomes a more and more acute threat," US Deputy Secretary of State Tony Blinken said in Seoul last week.

Whatever the outgoing administration's policy was with regard to curbing the North's nuclear ambitions, it has clearly failed.

The question for the incoming administration, whether headed by Hillary Clinton or Donald Trump, is why it failed and, more urgently, what to do about it.

The one thing the new president will not lack is vocal advice from any number of think-tanks, policy wonks, former diplomats and retired generals who believe they have the solution.

The last few months have witnessed an avalanche of op-eds, research papers and studies laying out the path the new White House incumbent should take and issuing dire warnings about the disastrous consequences of doing otherwise.

- Ahead of the curve -

"The first hundred days in office will be critical," said Joel Wit, a senior fellow at the US-Korea Institute at Johns Hopkins University.

"Rather than wait for events on the ground to narrow down choices and dictate policy, the new administration needs to get ahead of the curve. It needs to shape events itself -- not be shaped by them," Wit told AFP.

The policy argument essentially pits those who favour threatening the North Korean regime's very existence with crushing sanctions backed by military threat, against those who prefer a cocktail of measures in which tough sanctions and military strength provide a base for offering talks and incentives to denuclearise.

Some analysts say the debate smacks of desperate "do-somethingism" and suggest that dealing with the North Korea threat should be more about problem-containment than problem-solving.

In a stark assessment delivered to a Washington think-tank last week, the US Director of National Intelligence James Clapper said convincing North Korea to abandon nuclear weapons was "a lost cause".

As secretary of state, Hillary Clinton followed the Obama administration's sanctions-based policy of "strategic patience" -- refusing to talk with the North unless it takes steps to denuclearise.

Critics say that boiled down to sitting back and watching North Korea's nuclear weapons programme slip into high gear.

- Tough choices -

Those who back dialogue include Jane Harman and James Person of the Woodrow Wilson International Center for Scholars who wrote a recent op-ed in the Washington Post titled: "The US Needs to Negotiate with North Korea."

They argued for entering into direct talks with the stated goal of negotiating a freeze of all North Korean nuclear and long-range missile tests.

Negotiations would then move towards verifiable dismantlement, with Washington offering possible concessions such as a non-aggression pact or a suspension of joint military exercises with South Korea.

"Done right, there is a way out of the insanity," they wrote.

The opposite view was put in a briefing paper from the Brookings Institution that called on whoever the next president might be to "steer clear of illusory outcomes that offer no hope of success".

The paper advocated intensified sanctions -- backed by "a strong foundation of military measures" -- that would starve the regime of foreign currency, cut Pyongyang out of the international financial system, and squeeze its trade networks.

"The next president should make clear to Pyongyang that the United States is prepared to put at risk the one thing that North Korea holds even more dearly than its nuclear weapons -- the preservation of its regime," it said.

- Lack of experience -

Analysts say the gamut of opinion on North Korea runs particularly wide, given the lack of verifiable intelligence on, or real understanding of, a country that remains remarkably isolated.

"There are a lot of myths and misconceptions that have taken hold in the minds of people, and these are very difficult to counteract," Wit said.

"In any new US administration there will be people making decisions who have no direct experience of dealing with North Korea -- who have never even met a North Korean.

"Can you imagine a similar scenario when it comes to making decisions about somewhere like Russia?" he said.

The only real area of consensus on North Korea is that time is fast running out.

Its nuclear and missile testing programme has accelerated to the point where previous estimates -- once seen as alarmist -- that it could have an intercontinental ballistic missile capable of delivering a nuclear warhead to the United States by 2020, are now seen as soberly prudent.