A new U.S. ambassador arrived in South Korea Thursday pledging to do his utmost to upgrade relations between the two countries.

Korean-born Sung Kim is the first Korean-American to be named to the post since diplomatic relations were established 129 years ago. The former State Department official served previously as Washington's envoy to six-nation talks on North Korea's nuclear programs.

He said on his arrival that he expects the nuclear issue to play a big part in his work in Seoul.

But he declined to make predictions on the progress of talks aimed at re-starting the negotiations.

When asked about the talks, he said the key thing is for Washington and Seoul to make sure both are sending the same message.

There has been a flurry of diplomatic activity in recent months as countries seek to agree on terms for a resumption of the talks, which have been deadlocked since 2008.