Peter Harrell of the U.S. State Department, arrived in Seoul on Monday.
Harrell's visit comes as the U.S. and the EU are about to step up sanctions against Russia in the wake of the downing of a Malaysian civilian airplane by pro-Russian militants in Ukraine.
A government official said Harrell will brief government officials and bankers here on Tuesday morning about Washington's sanctions policy against Iran and Russia.
Harrell deals with economic sanctions and counter-threat finance at the State Department.
"Washington wants us to partially join sanctions on Russia or at least refrain from strengthening cooperation with Russia," the official added.