Hu's two-day visit comes less than 24 hours after the closing of the Beijing Olympics and as regional powers press North Korea to accept a nuclear inspection system as part of a disarmament deal the secretive North struck with five countries.

"We believe the visit will be a turning point in the two countries' relationship, which has been primarily an economic one, to expand into all areas, including politics, defence and culture," an official at the South Korean presidential Blue House said at the weekend.

The two sides have discussed a free-trade deal, but Seoul has been wary of initiating formal talks because of the potential flood of cheap farm products. It is not on the summit agenda.

China, the North's main benefactor, is also South Korea's largest trading partner with $145 billion (79 billion pounds) in annual two-way trade, according to official South Korean data.

In late June, North Korea presented a long-delayed account of its nuclear weapons programme at six-nation talks, hosted by China, that contained information about its plutonium production.

Russia, the United States, Japan and South Korea are also members of the six-way talks on the North's nuclear programme.

Hu and President Lee Myung-bak, who met in Beijing in early August before the Games' opening, will also discuss ways to combat dust whipped up by sandstorms in the Gobi Desert that mixes with pollution in China and fouls the air over the Korean peninsula each year.

They are scheduled to sign agreements on cooperation in energy conservation, promoting trade and technological research, and improving the safety of food being traded between them.

Hu leaves for Tajikistan on Tuesday for a summit of the Shanghai Cooperation Organisation, a regional security forum that includes Russia. The trip will take him to Turkmenistan later.