Washington ? The Obama administration’s approach toward North Korea has been described as “strategic patience.” A more accurate evaluation of U.S. policy would be “failure.” The administration has alternately wooed and threatened North Korea for four years, with no discernible effect.

Here’s what failure looks like: Since President Obama took office, Pyongyang has conducted several missile tests and two nuclear weapons tests, the most recent on Feb. 12. When the international community has tried to hold Pyongyang accountable, the regime has become even more erratic.

North Korea’s latest reckless action came this week, when it nullified the 60-year-old armistice that ended the Korean War, and cut its hotline with U.S. forces in the South. This was Pyongyang’s way of protesting the U.N. Security Council’s unanimous decision to impose new sanctions after last month’s nuclear test. Perhaps it was also a way of hazing South Korea’s President Park Geun-hye, who took office two weeks ago.

What’s next? Unfortunately, the only thing that’s predictable about North Korea is its belligerence. Pyongyang has taken violent actions in the first months after the election of each South Korean president since 1992, according to Victor Cha, a Korea expert at the Center for Strategic and International Studies.

What happens when diplomacy fails? This is the most disturbing problem in international relations, and it’s posed now by North Korea: How should the international community respond when a nation consistently ignores red lines? What policy options exist when patience finally runs out?

Tom Donilon, the national security adviser, had some newly tough words for Pyongyang in a speech Monday to the Asia Society. “The United States will not accept North Korea as a nuclear state; nor will we stand by while it seeks to develop a nuclear-armed missile that can target the United States.” But what does this language mean? The North already is a nuclear state, and it is developing missiles that could strike the U.S. with miniaturized warheads.

“North Korea will have to change course,” Donilon insisted. Otherwise, it will face more sanctions and new U.S. defense moves aimed at countering a “grave threat to the United States and our allies.” But what if North Korea doesn’t bend? One result will be more aggressive defense policies from South Korea and Japan, complicating security in Asia.

The North Korea problem is scary because its leadership seems to get more volatile over time. Kim Jong Eun, the new leader, “quickly consolidated power” after the death of his father, Kim Jong Il, in December 2011, according to U.S. intelligence. But some U.S. analysts believe the new president is more unpredictable and provocative than was his father.

Through two administrations, the underlying U.S. strategy toward North Korea has been to seek China’s help in containing this destabilizing force in northeast Asia. But this policy, too, has largely failed and the U.S. should be running out of patience. With depressing consistency, China has failed to step up to its responsibilities as a regional superpower. It doesn’t like the mercurial North Koreans, but evidently it even more dislikes taking action to restrain them.

Will China’s new president, Xi Jinping, lift Beijing’s game by dealing more aggressively with North Korea? Some analysts see signs of a toughening Chinese stance in recent articles published in the English-language newspaper owned by the official People’s Daily. Xi is also assembling a team, including Yang Jiechi, the top foreign-policy official, and Wang Yi, his successor as foreign minister, who are thought to favor more emphatic negotiations with Pyongyang, such as the so-called Six-Party Talks that took place from 2003 to 2009. The fact that China worked closely with the U.S. in drafting the latest U.N. sanctions resolution is also taken as a positive sign.

Some longtime Korea watchers argue that Kim is rattling sabers to get attention and that Washington should give it to him. “Even if we’re at an impasse, there has to be dialogue,” argues Joseph DeTrani, a former special envoy for negotiations with North Korea.

But when a country is developing nuclear weapons that could hit U.S. territory, and when its party newspaper responds to sanctions by calling for a “final showdown,” the U.S. needs options beyond diplomacy and the threat of more U.N. sanctions. So it’s reassuring that the U.S. Navy is readying ballistic missile defenses in the Pacific, and that it has such total dominance underwater that it can threaten any adversary in Asia instantly.

Counting on North Korean restraint has been a bad bet. It may be wiser to assume the worst, and plan accordingly.