Oil embargo could add fuel to the fire

And whether Pyongyang's key ally China would ever be willing to back such a move at the United Nations Security Council -- where it is a veto-wielding permanent member -- let alone enforce it, is also in doubt.

China is by far its biggest trading partner, responsible for around 90 percent of its commerce.

But Chinese Customs have not reported figures for crude oil exports to the North since 2014, shrouding the situation in secrecy.

The US Energy Information Administration (EIA) says estimates suggest Pyongyang imports about 10,000 barrels of crude oil a day, almost all of it from China and going to its sole functioning refinery, the Ponghwa Chemical Factory.

At a world market price of $50 a barrel, that would be worth around $180 million a year.

In addition, according to figures from the International Trade Centre, a joint World Trade Organisation-United Nations agency, the North imported $115 million-worth of refined oil products -- which could include petrol and aircraft fuel -- from China last year. Another $1.7 million-worth came from Russia.

A ban on supplies would be devastating for ordinary North Koreans, the Nautilus Institute think tank said in a report.

"People will be forced to walk or not move at all, and to push buses instead of riding in them," said the document by Peter Hayes and David von Hippel. "There will be less light in households due to less kerosene."

The ban will lead to "more deforestation", they warned, as North Koreans will be forced to cut down trees to produce charcoal, leading to "more erosion, floods and more famine" in the already impoverished country.

But Pyongyang, which embraces a "Songun" or "military-first" would immediately restrict supplies to private citizens, they said, and a ban would have "little or no immediate impact" on the North's army or its missile and nuclear programmes.

The military, which uses about a third of North Korea's oil supplies, has stockpiles for at least "a year of routine, non-wartime usage", they said, and could fight for about a month before running out of fuel.

Oh Joon, a former South Korean ambassador to the United Nations, told AFP that a suspension of oil imports would be "fatal" to the North.

"But it won't be easy to get China to agree" to such a move, he added.

Lips and teeth

At the United Nations, diplomats say the US wants to target oil, tourism and North Korean labourers sent abroad in a new set of Security Council sanctions -- which would be the eighth imposed on the country.

South Korean PresidentMoon Jae-In has called for an oil ban to be seriously considered, and Japanese Prime Minister Shinzo Abe has also backed stronger measures.

China is yet to be drawn, and Russian President Vladimir Putin dismissed further measures as "useless", while warning of the risk of "global catastrophe".

Beijing fears a collapse of the regime in Pyongyang that could send refugees fleeing over its border, and -- worse -- see US troops stationed on its frontier in a unified Korea.

"If oil is cut off, that risks the regime falling," said Jean-Vincent Brisset, a researcher at the Institute for International and Strategic Affairs in Paris.

The relationship between Beijing and Pyongyang was forged in the blood of the Korean War, when Mao Zedong sent millions of "volunteers" to fight US-led United Nations forces to a standstill.

Mao described them as close as "lips and teeth", and China has long been accused of failing to enforce sanctions even after voting for them at the UN.

But Beijing has become increasingly exasperated with its neighbour.

Former South Korean vice foreign minister Kim Sung-han said: "Regime collapse means China will lose all its strategic interests in having North Korea as a buffer state."

The only way to persuade Beijing to embrace and enforce an oil ban would be if its own interests were threatened, such as by US secondary sanctions targeting its banks and businesses, he said.

"China will only consider it if it's pushed to a dead-end by the US."

That would infuriate Pyongyang, said Wang Dong of the School of International Studies at Peking University.

"If China cuts the supplies, North Korea may show very fierce resistance," he said. "The situation on the peninsula would also deteriorate sharply."