South Korean President Lee Myung-bak will this week ask China's leaders to use their influence to lean on North Korea to show restraint amid a delicate transition to a new leadership.

Lee will hold a summit with China's president, Hu Jintao, in Beijing and will discuss ways to develop the strategic partnership between the two nations and cooperative measures for peace and stability on the Korean Peninsula, the South Korean president's office said in a statement.

Lee's three-day trip to China, his second in four years, starts on Monday.

The South has said its primary foreign policy goal this year is maintaining stability on the divided peninsula as its unpredictable neighbour embarks on a third generation of dynastic rule following Kim Jong-il's death last month.

Little is known about Kim's chosen successor, his son Kim Jong-un, who in his late 20s and who will be relying on a coterie of trusted members of the military and political elite to act as minders while he cements his grip on power.

Both South Korea and the United States have urged China, the North's main ally and benefactor, to help restrain the new leadership from staging any hostile acts.

Analysts say the young Kim may order a provocation, such as a small scale military attack or nuclear or missile test, to burnish a hardline image with the powerful military.

Over the past week, the North, which has twice tested nuclear devices, has stepped up its use of hostile language against the South.

China voiced its support for the North's new leadership soon after Kim's death was announced.

South Korea's ambassador to China, Lee Kyu-hyung, said last week that the South would continue to raise the issue of China's unwillingness to condemn North Korea when it provokes the South.

PROBLEMATIC

In 2010, South Korea criticised China for refusing to censure North Korea for torpedoing a South Korean warship, killing 46 sailors. The North denied it sank the vessel.

It is problematic because China has appeared to take an attitude of protection and support for North Korea, while the North sometimes makes military provocations and implements some incorrect policies, Ambassador Lee Kyu-hyung told the South's Yonhap news agency.

South Korea would continue to raise the issue and make efforts to persuade China to change that attitude, he said.

China backed North Korea during the 1950-53 Korean War while the United States fought for the South. The United States still has about 28,000 troops in South Korea.

Lee and Hu are also expected to discuss how the two nations will push preliminary talks to launch formal negotiations for a free trade agreement.

Since 2008, South Korea and China have held a series of joint feasibility studies on a possible free trade deal and reached an agreement to exchange their views on sensitive issues.

The two leaders will also discuss the rising number of Chinese fishing boats caught illegally fishing off South Korea's west coast. Last December, a South Korean coastguard was killed while trying apprehend a Chinese vessel.

(Editing by Robert Birsel)