Hong also held a separate one-on-one meeting with National Security Advisor H.R. McMaster to discuss pending issues between the two countries, including nuclear and missile tensions with North Korea and the deployment of the US THAAD missile defense system.

On Thursday, Hong, a former newspaper president who served as South Korea's ambassador to the US in 2005, visited Congress for a series of meetings with senators and congressmen who have played key roles in enhancing relations between the two countries.

Hong began the meetings with Sen. Cory Gardner (R-CO).

"It was an honor to welcome Dr. Hong Seok-Hyun to the United States to congratulate President Moon on his election and to discuss the historic alliance between our nations," said Garner, chairman of the Senate Foreign Relations Subcommittee on East Asia, in a statement.

"The ROK-US alliance is forged in blood and I reiterated to Dr. Hong that America's commitment to stand by our ROK friends against all external threats is unwavering. I look forward to working with President Moon Jae-In, Dr. Hong Seok-Hyun, and Ambassador Ahn (Ho-young) in the months ahead to strengthen our alliance and friendship," he said.

Gardner has been a leading voice in Congress for stronger relations between Washington and Seoul and greater pressure on Pyongyang. He is the author of last year's landmark North Korea Sanctions and Policy Enhancement Act that authorized significant sanctions on Pyongyang for its nuclear and missile development as well as human rights violations.

Hong was scheduled to meet with Sen. Ben Cardin (D-MD), ranking member of the Senate Foreign Relations Committee, as well as with Rep. Ed Royce (R-CA), chairman of the House Foreign Affairs Committee, as well as Rep. Ted Yoho (R-FL), later Thursday.

On Friday, he plans to meet with leading academics and experts on Korea-US relations. (Yonhap)