Does China hold the key to solving the N Korea crisis?

US Secretary of State John Kerry was in Beijing to meet the Chinese leadership, which has in his words "more capacity to make a difference" in the search for a solution to the current escalation in the Korean confrontation.

Before leaving Seoul on his trip to Asia he said he wanted to see Beijing "put some teeth" into the way the Chinese government deals with North Korea.

Well he got plenty of polite smiles today as he met China's new President Xi Jinping, but what can he really expect Mr Xi to do when it comes to dealing with Kim Jong-un?

Senior diplomats with experience of the relationship tell me that China's influence is less than we'd like to believe.

The reason being that the North Korean leadership knows it can stretch the historic links between the two Communist one party states very far. Chinese leaders have often been privately irritated by the threats made and uncertainty caused by Pyongyang.

We got a hint of that from leaked US diplomatic cables a few years ago which, if genuine, revealed that Chinese senior officials had described the North Koreans as behaving like a "spoilt child".

So although Beijing is believed by diplomats to exchange strong words with North Korean leaders, most recently after the rocket launch and nuclear test; Kim Jong-un knows that China will not ultimately do anything that would lead to the collapse of his regime. North Korea exploits that position. It can push China a long way before a serious split occurs.

So Mr Kerry today was trying to convince the Chinese into tougher tactics when it deals with its neighbour. China has immense leverage, supplying food and fuel as well as political protection. Withdraw Chinese support and the North Korean regime would be crippled.

However, the Chinese have a long standing public foreign affairs position, often stated, that it does not interfere in the internal affairs of other countries. Beijing could never change its policies or act in a different way just because the US urges it to.

It's simply unrealistic to think that John Kerry could tell the Chinese what to do and how to do it. Domestically the Chinese leadership cannot be seen to be acting on US orders. All he could do today was ask politely and hope for the best.

So what he got was the reiterating of the positions long shared by both China and the US: denuclearisation of the Korean peninsular. This suits the Chinese because they don't want US nuclear missiles stationed in South Korea close to China's border and the US doesn't want the North Koreans to end up with nuclear weapons for all the obvious reasons.

So today's meeting to some extent exposes the limited control the Chinese have over North Korea, as well as the lack of influence Washington has in Beijing when it comes to the search for a solution to the confrontation.