BEIJING, May 19 (Reuters) - China has used various diplomatic channels to warn North Korea not to conduct a fourth nuclear test, multiple China-based diplomatic sources told Reuters, after the reclusive state renewed its threat of "counter-measures" against perceived U.S. hostility.
North Korea, which regularly threatens the South and the United States with destruction, is already under heavy sanctions imposed by several U.N. resolutions beginning in 2006 but has defied pressure to abandon its missile and nuclear programmes.
It last conducted a nuclear test in February 2013.
"China has told North Korea that there is no justification for a new nuclear test and that they should not do it," said a Western diplomat who was briefed by Chinese officials.
The sources said China had used diplomatic channels in Beijing and Pyongyang to convey its anxiety about the possibility of a fourth test to the North.
China is North Korea's most important diplomatic and economic ally, though three nuclear tests and several rounds of sabre rattling have tested Beijing's support.
The United States has said it hopes China will use its influence to coax the North to abandon its banned nuclear weapons program. In recent public statements, Chinese foreign ministry officials have repeatedly called on all parties to "exercise restraint" on the Korean peninsula, without pointing the finger at North Korea alone.
China signed on to tougher U.N. sanctions last year after the third nuclear test, but has come under criticism from western countries and independent experts for failing to properly implement them.
North Korea's official Rodong Sinmun newspaper said this month the country was justified in using all available means at its disposal to counter aggressive challenges by the United States and South Korea aimed at stifling its sovereignty. (Reporting By Megha Rajagopalan, additional reporting by Ben Blanchard; Editing by Nick Macfie)