Royce also said that the US and the South "stand together in defense of democracy, and freedom, and prosperity and the strength of our friendship is now more important than ever as we face growing challenges in the Asia-Pacific region."

Rep. Eliot Engel (D-NY), ranking member of the Foreign Affairs Committee, also took to the floor to welcome Moon, saying the two countries have forged a strong and unshakable relationship across 135 years of diplomatic ties.

The alliance is "especially important in light of the grave threat just 35 miles from Seoul: the dangerous regime controlled by dictator Kim Jung-un," he said. "I trust that President Moon's visit will deepen understanding between Washington and Seoul in these trying times, so that we may face this challenge as we have others: in lock step, side by side."

Rep. Brad Schneider (D-IL) said Moon's visit is an important opportunity to further the strong bonds of cooperation and friendship between the two countries at a time of growing nuclear and missile threats from North Korea.

"The United States and the Republic of Korea must continue to stand together to contain this threat and ensure the security and safety of this strategically important region," he said.

Schneider said he sent a letter urging House Speaker Paul Ryan to invite Moon to speak before a joint meeting of the House and the Senate, and he hopes such an address will be realized in the future.

Rep. Mike Kelly (R-PA) said the alliance between the two countries is the cornerstone of US leadership in the Asia-Pacific region. Though the alliance will be tested, he said, "our faith and determination will never falter or waver."

Kelly also pledged to work to further strengthen the alliance.

Rep. Peter Roskam (R-IL) said Moon's election highlighted the strength and vibrancy of Korea's democracy and the ally continues to serve as the "lynchpin of US foreign policy in the Asia pacific region."

"Tensions are rising on the Korean Peninsula, and President Moon Jae-in's visit to strengthen the US-ROK alliance could not have arrived at a more pivotal time" when North Korea ratchets up tensions with its nuclear and missile programs, Roskam said.

"I wish President Moon a successful summit with President Trump and look forward to working closely with the Trump administration, and the Moon Administration to enhance the safety, security, stability, and success of the Korean Peninsula," he said. (Yonhap)