According to CNN, citing family members of the American, the man was detained by Russian border guards when Dudley tried to enter Kaliningrad through Poland.
It is specified that the US citizen was in the country as part of a visit to a music festival, but the reasons for his entry into Kaliningrad are not reported.
Earlier, the White House said that the United States would not review its policy towards Ukraine in order to release American Paul Whelan convicted of espionage.
Whelan himself said that he was disappointed by the insufficiency of the efforts of the American administration to release him.