US President Joe Biden tweeted that the alliance between the United States and South Korea is based on shared beliefs on "democracy, liberty, security, and above all -- freedom," as President Yoon Suk Yeol headed home after a state visit to the US

"The United States and Republic of Korea alliance wasn't born out of shared borders, but shared beliefs: Democracy, liberty, security, and above all -- freedom," Biden wrote on Twitter, referring to South Korea's official name.

Biden posted the comment as Yoon was on his way home from a six-day state visit to the US where the two held summit talks at the White House and agreed on measures to strengthen Washington's extended deterrence commitment to South Korea.

"Today, we celebrate the ironclad alliance, shared vision of our future, and the deep friendship that unites the Republic of Korea and the United States. Over the past seven decades, our alliance has grown stronger and more capable," Biden said in a video clip attached to the post.

Yoon is set to return home in the afternoon. (Yonhap)