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The Trump administration's primary North Korea strategy would do little to curb the country's nuclear program and could trigger a famine, according to experts.

After spearheading several rounds of sanctions, the White House is now urging China to turn off oil supplies to Kim Jong Un's regime and the 25 million people he rules.

Lt. Gen. H.R. McMaster, President Donald Trump's national security adviser, summed up Washington's thinking Sunday: "You cannot shoot a missile without fuel."

Many analysts say such a move would have minimal impact on North Korea's nuclear and missile programs and would instead hit the country's agricultural sector, potentially leading to mass starvation.

Freight trains carrying crude oil bound for North Korea from Chinese border city of Dandong. Kyodo News via Getty Images file

"If it could be done, a full oil cutoff would certainly dramatically reduce the amount of domestically grown food available to the civilian population," according to David von Hippel, a senior associate at the Nautilus Institute for Security and Sustainability, a California-based think tank.

Von Hippel warned the results of an oil embargo — which he conceded would be almost impossible to enforce — could have a catastrophic impact on a humanitarian level.

"Unless China or the rest of the world exported or gifted food to the DPRK to compensate, this would likely lead to famine," he added, referring to the North by its official name, the Democratic People's Republic of Korea.

North Korea's population would feel a lack of oil more acutely than most countries.

Much of the country's 46,000 square miles, an area around the size of Pennsylvania, is covered in mountains. According to the CIA World Factbook, only around 22 percent of North Korea is used for agriculture, compared with 44 percent of the United States.

What arable land there is, North Koreans farm intensively. They've also come to rely on tractors, irrigation pumps, refrigerators and transportation trucks to harvest and distribute food before it rots.

Von Hippel said that even without further sanctions, measures imposed in September as a result of Kim's missile and nuclear tests would likely impoverish North Korea's breadbasket.

"The civilian population will certainly feel the burden of the sanctions well before the nuclear weapons or missile programs or the DPRK elites do, if these noncivilians feel them at all," he said. "At some point, however, the agricultural sector will feel the pinch of sanctions."

Related: North Korea says war with U.S. is inevitable

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Elizabeth Rosenberg, a senior fellow and the director of the energy, economics and security program at the Center for a New American Security, a Washington think tank, said that famine is "among the possibilities" that lawmakers should consider when deciding whether to impose tighter trade restrictions.

"On the other hand, bringing many, many more people under grave threat from more and more intercontinental ballistic missiles tipped with nuclear warheads is a sobering thought," she said, acknowledging the balancing act that those involved in implementing sanctions often face.

A man carries a sack of containing Red Cross rations near a distribution center in Tongsin, North Korea, on May 31, 1997. LASSE NORGAARD - Red Cross / AP Photo, file

There is no need to imagine what widespread starvation in North Korea might look like. From 1994 to 1998, the country was ravaged by a famine that killed an estimated 1 million people.

Mirroring the current crisis, one of the contributing factors was a lack of oil-based products in the agricultural sector after the collapse of the Soviet Union in 1991.

Since then, life for many North Koreans outside the capital of Pyongyang has remained an impoverished and isolated existence. Even without a full oil ban, some experts say these people have suffered the most from the sanctions already imposed this year.

In September, the United Nations Security Council capped North Korea's crude oil imports at current levels and capped refined petroleum imports to 2 million barrels per year.

The U.S. wanted a total ban on all oil-based products, but this was dropped to keep China and Russia on board.

The loopholes in the current sanctions regime mean that China can keep pumping an estimated 10,000 barrels of crude oil into North Korea annually through the so-called Friendship Pipeline under the Yalu River.

The crude is then sent to North Korea's sole working oil refinery, the Ponghwa Chemical Factory, where it can be turned into products for military use but also — crucially for the civilian population — transportation, agriculture and the fishing industry.

Crude oil tanks in a suburb of Dandong, China, which is located on the border with North Korea. Kyodo News via Getty Images file

Even if this crude stopped pumping, the North could produce other forms of hydrocarbons, such as melting coal to make up the shortfall, according to a September report by the International Institute for Strategic Studies, a London-based think tank.

Some also speculate Kim has been hoarding fuel reserves in anticipation of further sanctions.

If there was an energy drought, Kim would likely let his innocent civilian population bear the brunt rather than let it affect the weapons he believes are essential to stop the U.S. from trying to topple his dynasty, according to a paper Von Hippel co-wrote after the last round of sanctions in September.

"There is little evidence of any direct impact between oil constraints and the missile programs, at this moment," according to George A. Lopez, a professor emeritus at the University of Notre Dame.

"The poorest people that you don't see in Pyongyang, and everyone outside the city, would be short of heating oil this winter. And the reverberations in national agriculture come spring, summer could be devastating."

This prioritization would be business as usual for North Korea — one of the poorest countries in the world, but one that still manages to spend more than one-fifth of its GDP on its military, far higher than any other country.

North Korean soldiers and Pyongyang residents attend a rally on Dec. 1. KCNA via KNS / AFP Photo / Getty Images

As Russian President Vladimir Putin put it in September: "North Korea would rather eat grass than abandon its nuclear program."

Several experts told NBC News that a total embargo of oil-based products would be nearly impossible to achieve. Doing so would involve persuading China to acquiesce to Trump's demands while stopping all illicit smuggling into North Korea.

"It's very difficult to believe that a full oil embargo could be fully implemented," said Rosenberg, the Center for a New American Security analyst.

A total of 49 countries, including China, are failing to fully implement the sanctions that are already in place, according to a report by the Institute for Science and International Security published Tuesday.

Related: How North Korea recruits its army of young hackers

And that's without trying to police a total ban on all oil entering the isolated state.

"It's hard to think of how you could create a really watertight sanctions program," Rosenberg added.

So what can be done?

Both Rosenberg and Lopez agreed that the way forward is not in trying to limit the physical goods traveling in and out of North Korea but to restrict the financial transactions associated with them. These measures have increasingly cropped up in U.S. and U.N. resolutions, even if they don't appear to be the White House's main focus.

"Such financial sanctions are the wave of the present and future," Lopez said. "It's not just 'follow the money,' as they say, but cut off all the money, illicit and legitimate."