Lee is the first South Korean leader to visit Beijing in six years and his meeting with Xi on Monday came a day after the nuclear-armed regime in Pyongyang fired two ballistic missiles into the Sea of Japan.

The pair will meet for an opening ceremony and a summit before the signing of an agreement and a state banquet, Seoul has said.

The South Korean leader, accompanied by a delegation of business and tech leaders, hopes to secure pledges to expand economic cooperation with his country's largest trading partner.

He has previously called for South Korea and China to work towards "more horizontal and mutually beneficial" trade.

And he hopes to possibly harness China's clout over North Korea to support his bid to improve ties with Pyongyang.

"China is a very important cooperative partner in moving toward peace and unification on the Korean Peninsula," Lee said during a meeting with Korean residents in Beijing on Sunday, according to Yonhap news agency.

Xi and Lee last met in November on the sidelines of the APEC summit in the South Korean city of Gyeongju -- a meeting Seoul framed as a reset of ties after years of tension.

Seoul has for decades trodden a fine line between China, its top trading partner, and the United States, its chief defence guarantor.

And Lee's trip comes less than a week after China carried out massive military drills around Taiwan, the self-ruled island it claims as part of its territory.

The exercise, featuring missiles, fighter jets, navy ships and coastguard vessels, drew a chorus of international condemnation that Seoul has notably declined to join.

Lee also deftly stayed on the sidelines since a nasty spat erupted between Beijing and Tokyo late last year, triggered by Prime Minister Sanae Takaichi's suggestion that Japan could intervene militarily if China attacks Taiwan.

In an interview with Chinese state broadcaster CCTV on Friday, he said that he "clearly affirms" that "respecting the 'one-China' principle and maintaining peace and stability in Northeast Asia, including in the Taiwan Strait, are very important".