With tensions on the Korean peninsula soaring to include threats of nuclear war, frustration is mounting at what US policy experts see as the failure of all efforts to rein in North Korea.

Decades of threats have waxed and waned despite myriad attempts to reach out for talks or punish the regime, as seen recently in the tightening of UN sanctions.

North Korea watchers see a familiar pattern in which the state ramps up threats or takes actions such as missile launches or nuclear tests in a bid to show anger and force concessions from the United States.

Observers saw parallels between the latest crisis and 1994 when Pyongyang took on a bellicose tone as it faced pressure over its nuclear program at a time of political transitions in both North and South Korea.

The 1994 crisis ended when former US president Jimmy Carter flew to Pyongyang, setting the stage for a joint energy project that has been the inspiration for several initiatives since.

"I still don't find any of the latest North Korean rhetoric that shocking. It's perfectly predictable," said Joel Wit, a former State Department official who was in charge of implementing the 1994 energy agreement.

"The difference this time is that they have nuclear weapons," said Wit, now a scholar at Columbia University.

North Korea has threatened to attack the United States with nuclear weapons, although experts doubt it is able to. The United States, in turn, carried out runs by its nuclear-capable B-2 bomber as part of exercises with South Korea.

Other new factors in the latest crisis include question marks over North Korea's young leader Kim Jong-Un and growing unhappiness from China over its smaller ally's insolence.

Bruce Cumings, chairman of the history department at the University of Chicago and the author of several books on North Korea, said the 24-hour news environment had also changed the dynamics behind Pyongyang's threats.

"You get instant attention on the World Wide Web which is so different than when I used to read their Central News Agency reports in the early '90s that would come a week late through Tokyo and you never knew if anyone would pay attention," he said.

But Cumings said that North Korea's tactics followed a pattern dating to even before the 1950-53 Korean War, when the leadership would threaten to destroy the South's army.

"It is always the case with North Korea that when its back is put to the wall, it lashes out and it creates problems. It says: 'If you want to sanction us, this is what you're going to get'," he said.

Cummings warned that tensions "are inevitable as long as the United States and South Korea are not willing to engage with North Korea."

"The North Koreans go about things in the worst way -- they are their own worst enemy -- but they keep saying that they want to talk to the United States in particular," he said.

But President Barack Obama's administration has ruled out what is widely considered North Korea's main aim -- its symbolic recognition as a nuclear weapons state, seen by the regime as critical to ensure its survival.

The Obama administration, after long hesitation, last year sealed an aid-for-disarmament agreement with North Korea that fell apart in a matter of weeks after Pyongyang attempted to test a rocket.

The previous administration of George W. Bush similarly swung widely in its approach to North Korea. Bush famously grouped North Korea as part of an "axis of evil" and under his watch Pyongyang tested its first nuclear device.

But Bush, like Bill Clinton before him, tried late in his term to seal a historic far-reaching agreement with North Korea.

Some US conservatives criticized the Bush outreach and have called for an entirely new approach.

Representative Ed Royce, the Republican chairman of the House Foreign Affairs Committee, has called on the United States to avoid any future deals with North Korea and instead aim at toppling the regime.