Among all of the foreign-policy challenges facing the United States, dealing with the isolated, nuclear-armed state of North Korea may well be the thorniest. And that reality shapes our analysis of Barack Obama's 2008 promise to "continue to confront North Korea … with a stark choice: take verifiable steps toward denuclearization or face increasing isolation and costs from the United States and the international community."

In short, the United States has followed this policy to a T. But North Korea is no less threatening. It may be even more so.

According to the Nuclear Threat Initiative, North Korea is capable of enriching uranium and producing weapons-grade plutonium; it has deployed short- and medium-term ballistic missiles; and it has successfully launched long-range rockets. Notably, the country has tested nuclear explosive devices in 2006, 2009, 2013 and twice in 2016. So, since Obama took office in January 2009 and Kim Jong Un succeeded his late father in December 2011, North Korea has only upped the nuclear ante.

North Korea's fourth nuclear test in January of 2016 prompted stepped-up sanctions, implemented through the United Nations Security Council, including a resolution in late 2016 that put in place the Security Council's toughest sanctions regime has imposed in more than a generation.

Sanctions were also applied by the United States through the North Korea Sanctions and Policy Enhancement Act, which passed both chambers of Congress with almost no dissent in February 2016. As a result of this legislation, "the U.S. Treasury has imposed notable, unilateral financial isolation measures on North Korea," said Scott Snyder, director of the program on U.S.-Korea policy at the Council on Foreign Relations.

The administration says its diplomatic engagement at the UN, the sanctions, its "trilateral" work with South Korea and Japan, and cooperation with China -- including U.S. sanctions on Chinese entities supporting proliferation in North Korea -- has left North Korea more isolated than ever.

Independent experts don't disagree.

"Throughout the Obama administration, the United States has responded to each North Korea nuclear test with both greater sanctions and greater defense cooperation with South Korea to increase the economic and security costs to North Korea," said Robert S. Ross, an east Asian specialist with appointments at both Boston College and Harvard University. "It has also refused to make any overtures to North Korea, and it has maintained that it will not negotiate with North Korea until North Korea announces an end to its testing."

The idea undergirding the sanctions has been that tightening them will eventually compel North Korea to compromise. The problem is, there's wide agreement that it hasn't worked out that way.

"The increasing pressure has not resulted in the desired change in direction or lessening of North Korean commitment to nuclear development," Snyder said. "Instead, we have seen an increasing pace of activities designed to achieve the ability to strike at longer ranges with nuclear-tipped missiles. The failure to contain or reverse North Korea's nuclear program will be recognized as an area where the Obama administration has failed to make tangible progress, despite fulfilling its pledges to increase pressure on North Korea."

Ross said the Obama administration is just the most recent presidency that failed to make progress on North Korea.

U.S. policy "has failed since the 1990s, when Washington first observed North Korea's nuclear program and tried to prevent North Korea from developing nuclear weapons," Ross said. "Clinton, Bush, and Obama each had different approaches to North Korea, but they all failed. Despite U.S. efforts through successive administrations, North Korea is now a de facto nuclear power."

Ultimately, Obama gets credit for standing by his promises about what he would do to North Korea if it continued to pursue nuclearization. However, even sticking to the promise failed to curb North Korea's nuclear ambitions; if anything, the threat has grown. So we rate this a Compromise.

Democrats promised that a re-elected President Barack Obama would "confront” the socialist dictatorship of North Korea with a "stark choice” over its nuclear ambitions.

North Korea's young leader, Kim Jong Un, would need to take steps away from nuclear arms, or face "increasing isolation and costs.”

The Obama administration has followed that script — though so far, not to great effect.

Instead, under the junior Kim, the nation has launched a ballistic missile, set off nuclear blasts and over the weekend declared a state of war with South Korea.

(That's set off earnest discussion about how seriously to take threats from a regime that's regularly used them to extract resources from the international community.)

One of those nuclear tests was the night before Obama's State of the Union address in February 2013.

In response, he declared: "The regime in North Korea must know they will only achieve security and prosperity by meeting their international obligations.  Provocations of the sort we saw last night will only further isolate them, as we stand by our allies, strengthen our own missile defense and lead the world in taking firm action in response to these threats.”

Meanwhile, the U.N. Security Council has tightened sanctions, while an expert in U.S.-Korea policy with Council on Foreign Relations noted "a sustained high-level U.S. response.”

The effort has been "in overdrive in recent weeks,” wrote Scott Snyder, senior fellow for Korea studies and director of the program on U.S.-Korea policy.

For example, he wrote, national security adviser Tom Donilon "insisted that North Korea ‘change course" and engage in ‘authentic negotiations" while delivering a stark warning that North Korea would be held responsible for nuclear terrorism resulting from its proliferation.”

Still, there's much more that the United States and its allies could do to pressure the North Korean regime, said Henry Sokolski, executive director of the Nonproliferation Policy Education Center and a Pentagon expert in nuclear proliferation under the first Bush administration.

If they want to isolate the country's leadership, they shouldn't seek to negotiate, he said. The "lunatic regime” itself is the problem.

The U.S. and its allies should instead work harder to cut off illegal activity — such as the drug trade and counterfeiting — that North Korea uses to get its hands on hard currency, Sokolski said.

But new sanctions "at least make them tougher than their predecessors,” he said.

(The George W. Bush administration focused on enticing North Koreans back to six-party talks, which ultimately broke down.)

The question now, another expert in nuclear nonproliferation told PolitiFact, is whether the administration's policy gets "overtaken by events.”

"At some point, North Korea's nuclear development will advance to the point where denuclearization is no longer a realistic option,” said James Acton, a senior associate in the Nuclear Policy Program at the Carnegie Endowment. "Indeed, I would argue it's already there.”

Michael Auslin, an expert in Asian security for the conservative American Enterprise Institute, says the Obama team should abandon attempts to negotiate, declare North Korea a nuclear power and move to contain it.

The administration instead insists the "path to peace is clear.”

Deputy White House press secretary Josh Earnest laid out the choices for reporters aboard Air Force One on March 29.

"The bellicose rhetoric emanating from North Korea only deepens that nation's isolation,” he said. North Koreans "should abandon their nuclear program.”

"And upon doing so, they will be welcomed back into the international community,” he said.

Democrats promised during Obama's re-election campaign that the president would present North Korea with a "stark choice”: to denuclearize or face "increasing isolation and costs.”  North Korea hasn't taken steps to denuclearize — and it has faced ever tighter U.S. pressure and international sanctions. For now, we rate this promise In the Works.