In this file photo, Kurt Volker, US special envoy for Ukraine, speaks during a news conference in Kiev on July 27, 2019.
The State Department has not returned messages seeking comment.
The State Press, the school paper of Arizona State University, first reported the development.
CNN has reported that Ukrainian President Volodymyr Zelensky had joked with Volker about Rudy Giuliani, Trump's personal attorney, in a meeting before the phone call.
Volker later set up the meeting between Giuliani and a Zelensky adviser in an effort to get the Biden matter out of official talks.
There is no evidence of wrongdoing by either Joe or Hunter Biden. »