South Korea has complained that some of its companies doing business in China have faced discrimination in retaliation for the THAAD deployment.
"This year marks the 25th anniversary of the establishment of diplomatic ties between South Korea and China, and we need to respect the things that we have achieved", he said.
South Korea's new President Moon Jae-In dispatched Lee to Beijing in the wake of his election victory last week.
They were expected to discuss ways of containing North Korea's missile and nuclear weapons activities as well as the economic fallout over the deployment in South Korea of the USA missile defense system called THAAD.
Trump has said "a major, major conflict" with North Korea is possible and all options are on the table but that he wanted to resolve the crisis diplomatically, possibly through the extended use of economic sanctions.
"The DPRK [Democratic People's Republic of Korea] will bolster its self-defense capabilities as long as the United States continues its hostile policies toward the DPRK and imposes nuclear threats and makes blackmail", North Korean diplomat Ju Yong Choi told the U.N. Conference on Disarmament Tuesday in Geneva.
(Chinese) "We hope the new South Korean government realizes the problems both countries are facing and takes effective measures to remove such obstacles to put the development of bilateral relations back on track". It has retaliated against Seoul by suspending visits to South Korea by Chinese tour groups and trips to China by South Korean entertainers.
As for Moscow, Russian President Vladimir Putin said, according to AFP, that the most recent ballistic missile test was unsafe, but he also warned against attempts to "intimidate" North Korea.
The nose cone resembles that of the KN-08 ICBM the North is believed to be developing, and the lofted trajectory tests re-entry by putting the missile through extra stress, said Joshua Pollack of the US-based Non-proliferation Review.
"I'm a person who has some sort of obsession (to fulfill) what I have said", Moon was quoted by Chung as saying during the meeting at the presidential office.
Moon's spokesman, Yoon Young, said last week that the special delegation to Beijing would "exclusively discuss the THAAD and the North's nuclear issues".
The state news agency also said Sunday's launch tested the nation's ability to carry a "large size" nuclear warhead.
A special envoy to Russian Federation is expected to head to Moscow next week.
During the meeting with political leaders, Moon also proposed instituting a regular consultative body involving officials from the government as well as the ruling and opposition parties in an apparent bid to enhance cooperation with the opposition-led legislature.