China began preparing for a power transition in North Korea several years before Kim Jong-Il's death and will do its utmost to consolidate his inexperienced son's hold on power, analysts say.

North Korea's closest ally has long sought to bolster its unpredictable, nuclear-armed neighbour, and is particularly keen to avoid instability on its borders as it prepares for its own transition of power this year and its economy loses steam.

Analysts said the speed with which Beijing recognised Kim's son Kim Jong-Un as the new ruler and called for stability in North Korea indicated it was not taken by surprise by the announcement of his death, two days after it happened.

"It was almost as if the statement had already been drafted before Kim Jong-Il died and the Chinese just had to put the current date at the top and release it to the press," said Scott Bruce of the Nautilus Institute, a US-based research group.

"They have been preparing for this (Kim's death) with the North Koreans. Part of Kim Jong-Il's trips in the last three years appear to have been planning for his death and the succession process."

In his final years, Kim -- diminished by a stroke in August 2008 -- regularly visited China, the biggest provider of humanitarian aid to his impoverished country.

He travelled to the Asian giant four times in just over a year, until his last visit in the summer of 2011.

Rumours that he introduced his youngest son to Chinese leaders in June 2010 in Beijing have not been confirmed.

But Kim Jong-Un reportedly met a delegation of high-level Chinese officials in Pyongyang at the end of that year and Bruce said the delegation gave its blessing to "the hereditary succession to a third generation of the Kim family".

Analysts said China would keep a close eye on all official moves and declarations coming from North Korea, with which it shares a 1,400-kilometre (868-mile) border, and try to extend its influence there.

Beijing fears a collapse of the North Korean regime would bring "the possibility of refugees, loose nukes, regional economic chaos, and an uncertain disposition of US troops on the Korean peninsula", said John Feffer, co-director of US research group Foreign Policy in Focus.

Valerie Niquet, of the Foundation for Strategic Research -- a French think tank -- said North Korea was of "considerable strategic importance" for China, particularly as the "regional re-engagement strategy of the United States (in Asia)" went against Beijing's interests.

Niquet added China wanted to remain an "indispensable go-between" in international efforts to end North Korea's atomic activities and in long-stalled six-nation denuclearisation negotiations hosted by Beijing.

The talks are expected to be high on the agenda as South Korea's President Lee Myung-Bak holds talks Tuesday with China's Premier Wen Jiabao.

"China will do whatever it takes to help consolidate Kim Jong-Un's rule," Feffer said, such as helping the impoverished nation to develop its economy, crippled by energy and food shortages as well as international sanctions.

Kim's last trips to China included visits to special development zones or factories, indicating Beijing was keen to pass on the lessons of the highly successful opening up of the Chinese economy to the outside world.

"It (China) can pump enough resources and expertise into North Korea to get the country back on its feet," said Feffer.

China -- North Korea's primary provider of food, energy, consumer products and weapons -- had negotiated "good deals" on the extraction of natural resources such as copper, coal and even rare earths in exchange, he said.

Beijing has also obtained access to ports such as the one in Rajin, in North Korea's northeast, which gives it strategic access to the Sea of Japan for 10 years, Feffer said.

Trade ties between the two countries have also strengthened, reaching $3.1 billion in the first seven months of 2011, compared with $3.5 billion for the whole of 2010 -- which could be another way for Beijing to stabilise the nation.

"China does not want to see big problems coming out of North Korea, and is ready to support (the country) in its development and reforms so that it develops in a stable manner," said Jia Qingguo, professor of international relations at Peking University.

"Naturally, the Chinese government is worried, because Kim Jong-Un is young and lacks political experience," he said.

"For the moment, his power base is not strong. That's the most worrying."