Washington (CNN) White House trade adviser Peter Navarro on Thursday declined to answer questions about whether China opening an investigation into former Vice President Joe Biden and his son has come up during trade talks with the US.

"Did you bring up investigating the Bidens as part of the negotiations?" CNN's Jim Sciutto asked Navarro at the CITIZEN by CNN conference in New York.

"It's not an appropriate question in my judgment, OK," Navarro replied.

"It's an easy one for you to say no," Sciutto said, to which Navarro responded: "But you're asking me to violate a principle here."

"I'm not going to talk about that stuff. If I answer that question then you'll ask me another question," he added.

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