China has turned off the tap on crucial goods for North Korea in a bid to pile on economic pressure as South and North Korean leaders prepare for an unprecedented diplomatic summit this April, and hopes for May talks between the US the isolated country mount.

The leaders of North and South Korea are to meet on April 27 for the first time in more than a decade, the two countries announced on Thursday after preliminary talks between senior officials.

An analysis of Chinese customs data from Aberdeen Standard Investments has revealed that China’s exports of refined petroleum to North Korea have collapsed in the last five months, to as little as 3.7 per cent on the previous year.

Other products have also been hit. North Korean steel imports from China have fallen dramatically, along with car imports. Economists believe that the data may explain the recent dramatic shifts in North Korean policy.

The North Korean leader, Kim Jong-un provoked widespread international attention this week with a trip to meet Chinese President Xi Jinping in Beijing. This followed the country's attendance at the Winter Olympics, and was another highly unusual step for closed-off state, known for its efforts to proliferate nuclear weapons an oppressive regime.