President Lee Myung-bak thanked US Senator Webb during a meeting on Monday for the congressman's support in condemning North Korea over the Cheonan disaster.
Webb who is chair of the Senate Foreign Relations' Subcommittee on East Asia and Pacific Affairs played a key role in getting the Senate to adopt a resolution supporting South Korea and condemning North Korea over the ship's sinking.
The US official arrived in Seoul on Sunday for a three-day courtesy call.
Meanwhile, President Lee is set to attend the ninth Asia Security Summit in Singapore this week.
The South Korean leader is scheduled to leave on Friday for the Shangri-La Dialogue, where he will deliver a keynote speech on his government's evolving role on the international stage as well as address the current security situation in Northeast Asia.