Washington's chief negotiator for defense cost-sharing talks with Seoul arrived in South Korea on Sunday.
James DeHart will sit down with his South Korean counterpart Jeong Eun-bo on Tuesday and Wednesday for a fresh round of negotiations.
DeHart remained tight-lipped on whether the two sides have made any progress or whether the U.S. will be more flexible.
The two sides last met in Washington about two weeks ago.
The U.S. is reportedly demanding South Korea pay 5 billion U.S. dollars, a more than five-fold increase compared to Seoul's commitments under their current deal, which expires at the end of the year.