Two shipping containers full of hygiene kits languish for weeks in a Chinese port, unable to reach North Korea.

Key points: The latest round of sanctions prohibit iron, steel and other metals

The latest round of sanctions prohibit iron, steel and other metals The few charities still operating in North Korea face bureaucratic hurdles

The few charities still operating in North Korea face bureaucratic hurdles 70 percent of North Koreans suffer food insecurity

They are intended for people with tuberculosis or hepatitis, not to advance nuclear missile programs, but Chinese customs officers see something objectionable in the cargo: nail clippers.

As sanctions on Kim Jong Un's government intensify, the few aid groups operating in North Korea are facing sometimes bewildering economic restrictions and bureaucratic hurdles that could cripple life-saving work.

While the UN Security Council says the penalties should not affect humanitarian help, the Trump administration cites even North Korea's reported food and fuel shortages as evidence of a pressure campaign working.

The nail clippers were part of a consignment sent by Christian Friends of Korea, one of the few charities working in North Korea despite escalating nuclear tensions.

Two in five North Koreans are undernourished, according to CARE International. ( CARE USA )

The latest round of UN sanctions bans the supply of metal items, so that explains the clipper holdup, but it is not the only example.

The American Friends Services Committee, another aid group, is struggling to deliver agricultural equipment such as threshers, compost makers and shovels.

"Sanctions should not have an impact on the well-being of ordinary citizens," said Linda Lewis, a member of the Quaker committee that's helped North Korean farmers for two decades.

"This work should not be shut down for political reasons."

'Unavoidable outcome'

How do you pressure governments, short of war, to change their behaviour without unduly injuring innocent civilians?

That's one of biggest questions for the economists, foreign policy professionals and political leaders who devise and put in place economic sanctions around the world.

UN penalties routinely include broad exceptions for most basic civilian goods.

Even when the United States targets its most intractable foes, it exempts food, medicine and humanitarian supplies.

In the case of North Korea, which the US and others want to rid of nuclear weapons, it's unclear whether the right balance is being struck.

Citing reports last week from Tokyo of scores of North Korean fishing boats, with dead crews, drifting into Japanese waters, Secretary of State Rex Tillerson said the sanctions are "really starting to hurt".

Sorry, this video has expired Bodies recovered from suspected North Korean 'ghost ship' in Japan

The human suffering, he said, was North Korea's responsibility and an "unavoidable outcome" of its failure to help its own people.

Tillerson also doubted that humanitarian assistance, which South Korea is considering, would reach the right people in the North.

His remarks alarmed humanitarian advocates.

But given that the alternative to the US-led pressure may be military conflict, the Trump administration is getting much leeway from international partners and the public over how the sanctions are affecting North Korea's 25 million people.

No to shovels, spoons, paperclips

Three times in the past year, the UN Security Council has tightened economic restrictions on North Korea, cutting fuel supplies and banning trade in the goods that make up 90 percent of the North's export revenue.

The latest round, designed to punish a North Korean long-range missile test, prohibit selling the North iron, steel and other metals.

The new sanctions prohibit supplying any iron, steel or other metals which includes agricultural equipment. ( AP: Christian Friends of Korea )

That covers nearly 150 different categories of products, covering everything from stainless steel ingots to spoons and paper clips.

In the case of the nail clippers, Heidi Linton of the Christian Friends of Korea, which supports more than 30 tuberculosis and hepatitis care centers, said its routine shipment of hygiene kits was stuck this month in the northern Chinese port of Dalian for two weeks.

Finally, Chinese customs gave special permission for the shipment to proceed.

Without that decision, Linton would have had to pay people to individually unpack the metal nail clippers from several thousand kits for the two containers to be cleared.

For North Korea's civilians, the aid groups play a crucial role.

The UN works on child health care and provided food for more than 800,000 North Koreans last year.

"Sanctions may be adversely affecting that essential help," UN human rights chief Zeid Ra'ad al-Hussein told the Security Council last month.

70 per cent of North Koreans suffer food insecurity, and two in five are undernourished, according to the UN.

The aid group Care International calls it the world's most under-reported humanitarian crisis.

AP