China 'frustrated' by North Korea
5 April 2013 Last updated at 09:15 BST
With the rhetoric escalating in North Korea, attention is turning to China's role.
As one of North Korea's few friends, China has not been able to quell the tension, and China finds itself in a difficult position.
Shujie Yao, professor of economics and Chinese sustainable development at Nottingham University, explains that China wants to protect its neighbour, but is also disapproving and keen to change its behaviour.
Speaking to the Today programme's Evan Davis, Professor Yao said that "China is squashed in the middle... North Korea is not the right thing that people expect it to do."
First broadcast on BBC Radio 4's Today programme on Friday 5 April 2013.