SEOUL (AFP) - China's president arrives in Seoul on Thursday for a state visit focused on nuclear developments in North Korea, which has spent the past week playing hawk and dove with threats, missile tests and peace offers.
It will be Xi Jinping's first trip as head of state to the perennially volatile Korean peninsula, and his second summit with South Korean President Park Geun Hye who visited China last year.
North Korean leader Kim Jong Un is still waiting for an invite to Beijing - a perceived snub that speaks to the strained relationship between Pyongyang and its historic and most important ally.
In what some saw as a display of pique at Mr Xi's visit, North Korea conducted a series of rocket and missile launches into the Sea of Japan (East Sea) over the past week, triggering protests from Seoul and Tokyo.
The North has been in particularly mecurial rhetorical form of late, one day threatening a "devastating strike" against the South and the next proposing a suspension of all hostile military activities.
South Korea on Tuesday rejected the peace offer as "nonsensical" and suggested that Pyongyang show its sincerity by dumping its nuclear weapons.
Mr Xi and Ms Park will hold their summit after Thursday's official welcoming ceremony, and the two leaders are then expected to sign a joint communique.
Seoul will be hoping for a strong statement on North Korea's nuclear weapons programme, but analysts said Beijing was unlikely to up the rhetorical ante.
"That would go against China's traditional diplomatic pattern," said Dr Kim Joon Hyung, professor of politics at Handong Global University.
"Xi will probably keep to the general line of urging the denuclearisation of the Korean peninsula, rather than criticising the North directly," Dr Kim added.
As the North's diplomatic protector and chief economic benefactor, China has repeatedly been pressured by the international community to use its leverage to rein in Pyongyang's nuclear ambitions.
But while Beijing has become increasingly frustrated with the North's missile and nuclear tests, it remains wary of penalising the isolated state too heavily.
It is especially anxious to avoid any regime collapse that would result in a unified Korea with a US troop presence on its border.
Assistant Secretary of State Daniel Russel told AFP the visit showcased a "stark contrast to the chilly relationship between Beijing and Pyongyang."
"The Chinese have increasingly moved in the direction that denuclearisation is more than just a slogan, it is an objective that needs to be implemented," he said.
The wider background to Mr Xi's visit includes China's response to the US "pivot to Asia" and the battle between the two major powers for regional influence.
China is currently South Korea's largest export market and two-way trade stood at around US$275 billion (S$343 billion) last year, but analysts say Beijing wants to move beyond economic ties and promote political and security links.
"With China and the United States vying for influence in the region, South Korea has a lot of strategic value," said Jo Yang Hyeon, a professor at the Korea National Diplomatic Academy.
There are currently around 29,000 US troops stationed in South Korea which is also protected by the US nuclear umbrella.
The military ambitions of the other main US ally in the region, Japan, is also likely to figure in Thursday's summit talks, with both China and South Korea concerned by the recent change to its pacifist constitution.