Lee was named the top envoy to the US by President Moon Jae-in in August and was formally appointed last week following US consent early this month.

"For the last two years, South Korea and the US have been closely cooperating to turn the flow of history from conflict and confrontation to dialogue and peace on the back of diplomacy from the two countries' leaders," he said. "There are achievements, but since we still have a long way to go, I'll work with a vision to create a big stream of peace."

Lee, 70, has a sizable task ahead of him as Seoul and Washington face a number of bilateral and trilateral regional security issues, including the ongoing defense cost-sharing talks with Washington and a row with Tokyo over history and trade that led to Seoul's decision to terminate a military information-sharing pact with Japan. Lee said he believes those issues can be solved reasonably in the spirit of alliance.

Lee said he'll closely monitor the situation in the US, particularly Washington's relationship with Beijing.

"The US-China relationship can affect the international political environment, and since it plays a key factor to set coordinates for our diplomacy, I will watch it closely," he said.

"I'll also analyze how US domestic issues can affect our national interest."

Lee was South Korea's first chief nuclear negotiator for the six-party talks involving the two Koreas, the US, China, Japan and Russia when it was launched in 2003 with the goal of resolving the North Korea nuclear issue.

Asked about his thoughts on North Korea issues, Lee said he'll keep a level head, emphasizing that related parties should keep up their efforts and bear in mind that it is a "serious problem."

"What's important is preventing the situation sliding towards a war," he said. "That's what diplomacy needs to do. History of denuclearization diplomacy shows this is a matter that can't be solved in a quick time."

Lee said he can't make any prediction on whether the US and North Korea will resume their talks this year. Representatives from Washington and Pyongyang held their first meeting in seven months in Stockholm early this month, but the talks broke down again, with the North accusing the US of failing to come up with a new proposal.

Meanwhile, Lee began his duties as ambassador by visiting the memorial cemetery in Washington to pay tribute to late American veterans who fought in the 1950-53 Korean War. (Yonhap)