The extension was a fresh sign that discussions were moving in a positive direction as staff for the two sides meet face to face for the first time since President Donald Trump and his Chinese counterpart Xi Jinping agreed last December to restart talks, CNN quoted the spokesperson as saying on Tuesday.
China's Commerce Ministry said ahead of the meeting that it would last only two days.
The Trump administration, in its own notice announcing the US delegation, did not specify how long the visit would last, saying only that talks between the two countries were "beginning Monday".
An informed source told CNN that negotiators between the world's two largest economies needed more time to discuss issues that were part of the agenda.
The decision included long-awaited approvals by US farmers.
However, it currently remains unclear exactly how deeply negotiators have been able to delve into tougher issues including forced technology transfers and subsidies.
In addition to Gerrish, the official delegation will also include David Malpass, the Treasury Department's undersecretary for international affairs.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)