A North Korean nuclear bomb detonation is inevitable as the defiant Asian regime seeks further leverage against Washington and its allies in the region.

Experts told worried lawmakers Wednesday that President Barack Obama repeated mistakes and miscalculations made by Presidents Bill Clinton and George W. Bush. Unless the Obama administration ditches Washington's decades-old sanctions-based approach, the analysts told a House panel that Pyongyang will gain crucial leverage over the West.

"I think we will see a nuclear test" in the coming months, Michael Green of the International Assessment and Strategy Center said. Green sees several pieces of evidence that are the foundation of his warning: Recent images showing digging near a known nuclear facility, North Korean leaders' defiant rhetoric and the 100th birthday on the nation's founder, Kim Il-Sung.

"If I were I betting, I would say they will do it," Green said, adding that a successful nuclear explosion will give North Korea new ammunition in any future talks with U.S. and regional officials—Tokyo, Seoul and even Beijing—about its nuclear arms program.

North Korea already gained some leverage last week when it fired a rocket in defiance of Washington—but more importantly, it gained time and space to keep up its atomic arms and long-range missile work.

Frederick Fleitz, a former CIA officer and senior State Department official, puts the odds of a North Korean nuclear test at "50-50" in the next few months. But over a longer span, he said, "eventually there will be a test of that kind."

Fleitz also warned about future North Korean rocket and missile launches, saying regional tensions could further escalate if such a platform—potentially weaponized—landed in Japan, South Korea or even Hawaii.

Comments made by North Korean spokesmen and officials after Friday's failed rocket launch do give Fleitz hope "there's a line they aren't prepared to cross."

In the wake of the failed missile test, U.S. officials already are crafting a new sanctions package designed to punish Pyongyang. But experts say sanctions alone won't be enough to push North Korea to give up its nuclear work.

The U.S. and its allies "must move beyond sanctions," Patrick Cronin of the Center for a New American Security told the House panel. "We're losing leverage over North Korea," he added.

Cronin urged U.S. officials to pursue tactics like targeting the Chinese banks that do business with senior North Korean civilian and military leaders.