North Korea and its nuclear programs have been put on the back-burner for most of President Barack Obama's tenure. But dealing with the recalcitrant regime will likely be one of the foremost diplomatic issues for whoever occupies the White House next January, diplomatic watchers here say.

Both Democratic front-runner Hillary Clinton and de facto Republican candidate Donald Trump have said they regard the North's nuclear program as a big threat to U.S. national security and would handle it as an urgent issue.

"The North Korean nuclear issue is the biggest threat to the national security of the United States and is the foremost agenda item to be handled by the next president," said Jake Sullivan, top foreign policy advisor to Clinton, in his address to the Asia Society on Monday.

"North Korea's nuclear programs are a very big and serious problem," said Walid Phares, foreign policy advisor to Trump. In an interview with the Yonhap News Agency last week, Phares said: "The Barack Obama administration has been unable to solve the problem but the ‘Donald Trump administration' can resolve it by all means."

The two presidential hopefuls are poles apart on almost all issues but show considerable similarities on the North Korean nuclear problem.

Both call for "pressure" rather than "dialogue" as long as the North refuses to denuclearize itself and want to force the isolationist regime to change its attitude by using China, which exerts the biggest influence on Pyongyang.

A deeper look into their plans shows differences between how each camp views the North Korean nuclear issue and approaches it.

Clinton seems likely to follow the basic direction of the Obama administration's North Korea policy and resolve the North's nuclear problem in a similar way to that of nuclear negotiations with Iran. Trump, on the other hand, will step up the pressure tactic, with the help of allies and friendly nations, and use China to force Pyongyang to abandon its nuclear ambition. Trump's frequent change of words and his lack of concrete action plans are eroding the trust in his policy, however, the local observers say.

Clinton's application of the Iranian model to North Korea means she would tighten the reins of sanctions and pressure on the reclusive regime until it comes to the dialogue table on its own.

This appears to be little different from Obama's "strategic patience" but there is a clear difference: while Obama "outsourced" sanctions on the North to China, Clinton will pressure Beijing to join sanctions and, if necessary, apply a "secondary boycott" on Chinese banks and businesses that engage in business with North Korea.

If Clinton is elected, therefore, chances are high that top leaders of the U.S. and China will hold a parley on the North Korea issue. "The next U.S. president, when she or he holds the first summit with Chinese President Xi Jinping, should handle the North Korean nuclear issue in a most urgent and important way," Sullivan said. Given North Korea has an isolated economic system unlike Iran, however, the pressuring tactic's effects are yet to be known, the observers said.

Trump's strategy is also to "pressure China to pressure North Korea," and more so in that the real estate-mogul-turned-politician said he would be ready to wage an "economic war" with China for that purpose.

On Tuesday, however, Trump said in an interview with Reuters he was willing to meet and talk with North Korea's Kim Jong-un, seemingly breaking away from his previous indirect approach using China. Yet most experts, in Seoul and Washington, do not attach much significance to Trump's most recent remark, regarding it as the reiteration of a diplomatic principle that the door to dialogue is open to all.

A ranking North Korean official welcomed the Republican runner's remark.

"We do not care who will be the president of the United States, as long as he or she does not try to oppress us," said Yang Hyeong-sup, vice chairman of the standing committee of the North's Supreme People's Assembly. Asked to comment on Trump's remark during an interview with APTN, Yang said: "There will be nothing wrong with it."

A U.S. expert opposed the move, though. In a contribution to Foreign Affairs Wednesday, Michael Green, deputy director of the Center for Strategic and International Studies, advised against Trump's alleged intention to meet Kim, saying it would be tantamount to recognizing North Korea as a nuclear power while deepening the agonies of North Korean people suffering glaring human rights abuses under the three generations of dictatorship.