The Telegraph reports: There are clear signs that China is losing patience with North Korea, America’s former top diplomat in Asia has said.

For several decades, China has been North Korea’s closest ally, largest trade partner and primary source of aid.

However, Kurt Campbell, the former head of the State department in Asia, said there are signs that a relationship once described by Chairman Mao to be “as close as lips and teeth” is wearing thin.

“There is a subtle shift in Chinese foreign policy. Over the short to medium term, that has the potential to affect the calculus in north east Asia,” Mr Campbell said at a forum at John Hopkins university.

“You have seen it at the United Nations (Security Council). We have seen it in our private discussions and you see it in statements in Beijing,” he added.

Mr Campbell, who left the State department in February to found his own consultancy firm, was one of the architects of the US diplomatic and military “pivot” towards Asia.