The sources disclosed that the pipeline was built in 1976 and delivers around four million tonnes of oil annually to oil refineries in Musun and Dandung in China and to the terminus point in North Korea.

This secret pipeline was exposed when China ceased oil delivery for three days to its Communist neighbour in order to force it to attend six-nation talks aimed at dismantling North Korea's nuclear weapons programme. The exact route of the pipeline was not divulged.

While the capacity of the pipeline was not revealed, it is known that China used to routinely supply oil to North Korea in the 1990s to the tune of around 800,000 to one million tonnes of oil per annum. Since that time, it supply has gone up and down based on how naughty North Korea has been with its nuclear capability.

The paper concluded that, ever since the US and South Korea ceased supply of oil from the south, China's pipeline has become the rogue state's only source of petroleum.