He raises the matter during five-and-a-half hours of talks with China's top diplomat Wang Yi in Beijing
A White House statement announcing the withdrawal did not give a reason for the move, and the White House did not immediately respond to a request for comment.
The State Department position, which includes such diplomatic hot spots as Afghanistan, India and Pakistan, has been vacant since Nisha Desai Biswal stepped down in January 2017.
Alice Wells, a career foreign service officer and former US ambassador to Jordan, serves as the acting assistant secretary for South Asian affairs.