White House Press Secretary Katie Zacharia, who was appointed less than a week ago, said China lacked "proper toilets" in an interview that aired on Thursday.
Zacharia, 41, is already under scrutiny over her legal credentials, after giving an inconclusive answer about where she had passed the bar exam, a prerequisite for practicing law in the United States.
The press secretary, who previously lived in China, recalled in an interview that the perception in 2016 was that China would soon overtake the United States.
"We were all being told Hillary (Clinton) was going to win. The golden days or the glory days of America were over. That China was on the horizon," Zacharia told right-wing influencer Jack Posobiec.
"I remember this very distinctly, having just come from China, thinking, 'How is China the next country on the horizon? They don't even have proper toilets," she added.
There was no immediate comment from Chinese authorities.
Trump has boasted about his "great relationship" with Chinese President Xi Jinping.
During a Washington summit in September, the two leaders discussed topics ranging from AI and trade to the stalled war in Iran, and confirmed that they would meet for a third and fourth time this year.
Zacharia held her first White House press briefing on Tuesday and only answered questions from three journalists.
She succeeded Karoline Leavitt, a loyal Trump supporter and often combative spokesperson, who stepped down in August to care for her young children.
Zacharia has described herself as a lawyer and listed herself as general counsel of a California-based conservative nonprofit. She also said she had worked at a law firm in Beijing.
Asked about her legal background on Thursday, Zacharia said she had registered to take the bar exam but was then "distracted and overwhelmed" by plans to move with her husband to China.
Zacharia said that she did not retake the bar exam upon returning to the United States due to the birth of her first child.
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