South Korea's president arrived in Beijing Thursday for summit talks to be dominated by Pyongyang's nuclear programme, seeking to push China to do more to bring its wayward ally North Korea to heel.

"South Korean President Park Gyen-Hye arrived in Beijing to start a four-day visit to China," the state broadcaster CCTV said on an official news microblog account. She arrived late morning, it said.

Park -- who will meet her counterpart Xi Jinping on Thursday -- has said that her priority will be to "harden" China-South Korea cooperation on pressing for denuclearisation of the North.

Washington and Seoul have made it clear they will never accept the idea of North Korea as a nuclear state, and insist Pyongyang must show a tangible commitment to abandoning its nuclear weapons if it wants substantive talks.

Both have pressured China -- North Korea's sole major ally and economic lifeline -- to use all its leverage to rein in Pyongyang.

Park will be hoping her visit, which will be anxiously monitored by the regime in Pyongyang, will yield a strong joint statement that commits both sides to a denuclearised North Korea. But China is unlikely to go much further.

"China has traditionally emphasised the need to keep North Korea stable, while trying to solve the nuclear issue," said Choi Woo-Seon, a professor at the state-run Korea National Diplomatic Academy.

Pyongyang appears to have moderated its stance after a series of bellicose statements and gestures in recent months against Seoul and Washington, including threats of nuclear war.

While a planned meeting with South Korea fell through, it has offered direct talks with the United States, and has sent two envoys to Beijing in the past four weeks.

China's relationship with North Korea -- famously described by Mao Zedong as being as close as "lips and teeth" -- was forged in the 1950-53 Korean War which China entered to prevent the North's total defeat.

But it has weakened significantly over the years, as China's economic transformation has distanced it from the ideological rigidity of the dynastic Kim regime across the border.

In line with UN sanctions, Beijing has moved to restrict Pyongyang's financial operations in China which the international community says are the major conduit for funding its nuclear weapons programme.

During Park's visit, Beijing will also seek to strengthen the overall strategic relationship with Seoul, said Peking University professor of international relations Jia Qingguo.

China's relations with South Korea got off to a late start with diplomatic relations only established in 1992, but have improved steadily ever since, especially in the economic sphere.

China is now South Korea's biggest trade partner and Park will be accompanied on her trip by a sizeable business delegation. The two sides are expected to discuss a free-trade pact.

The strategic side of the partnership has always been coloured by the issue of North Korea and stagnated under Park's predecessor Lee Myung-Bak, who focused his efforts on boosting Seoul's alliance with Washington.

The hopes of a reboot have been bolstered by the fact that Park and Xi are both new leaders, having taken office within one month of each other earlier this year.

"China wants to attach a lot of importance to this relationship not just because of North Korea," Jia said. "The relationship deserves this kind of attention."

But he acknowledged that any improvement in China-South Korea ties would "impact the feelings" of North Korea.

"They are sensitive to events like this."