HANOI (AFP) - The second summit between United States President Donald Trump and North Korean leader Kim Jong Un failed to produce a deal on Pyongyang's nuclear programme, with the two sides at an impasse over the sanctions imposed on the North.
The cash-strapped regime has been under multiple United Nations sanctions for decades over its weapons programmes, and has blamed them for its economic woes.
At first, many of the restrictions were on technology that could be used for weapons development, but more recent measures have targeted some of its key economic sectors.
Here's a look at some of the sanctions.
In December 2017, the UN Security Council capped crude oil shipments to four million barrels per year, put a ceiling on refined petroleum products including diesel and kerosene to 500,000 barrels, and banned natural gas shipments.
North Korea has little oil of its own, relying on imports to keep its citizens and soldiers moving.
China and Russia - Pyongyang's main oil providers and both of them permanent members of the UN Security Council - voted for the limits in November 2017 after the North's sixth nuclear test and a series of missile launches.
Some have called the measure a jab at Pyongyang's "economic lifeline" but the cap was around the level of existing supplies, and critics note there are no means to check how much crude oil is delivered through the pipeline running from China to the North.
Crucially, the resolution includes an exemption for "livelihood purposes" - similar to clauses in past resolutions that have been used as loopholes.
Chinese Customs have not reported crude oil exports to the North for several years, but pipeline operator China National Petroleum Corporation had said in the past that it supplies 520,000 tonnes of crude each year.
According to figures on the UN sanctions committee's website, between them, China and Russia reported supplies of around 340,000 barrels of refined products to the North last year.
Coal and other commodity exports
The UN Security Council banned the North from exporting commodities such as coal, iron and lead in 2017.
Before the measure was imposed, North Korea reportedly earned around $200 million a year from the products - around 30 per cent of its exports by value.
The impact has been significant, and AFP reporters in the North have seen mountains of coal piled up on docksides, unable to be exported.
The South's central bank said trade with China - which accounts for 95 per cent of North Korea's external business - fell sharply in the first half of 2018.
But there have been successful attempts to evade the measures.
A UN report last year said deliveries of coal, iron and steel to China, India and other countries generated nearly US$14 million (S$19 million) for the North in just six months.
Imports and exports of textiles - both fabric and clothing - by the North are banned under the UN measures.
Textiles are one of North Korea's major businesses, with total exports estimated at around US$750 million in 2016, when they ranked as its second-biggest sales item, according to Seoul's Korea Trade-Investment Promotion Agency.
Chinese firms supply material to the North, where they are made into clothing in factories using cheap labour, and re-exported, mostly to China or Russia.
The resolution imposed in December 2017 ordered countries to repatriate tens of thousands of North Korean labourers working abroad when their contracts expire.
Their toil, mainly at construction sites in Middle Eastern countries as well as Russia and China, is considered a vital source of hard currency for Pyongyang.
Even before the UN measures, Pyongyang's use of overseas workers - known to work up to 12 hours a day but given only a fraction of their wages - was under scrutiny by the international community for human rights violations.