Prime Minister Erna Solberg was quoted as saying by the Norwegian news agency NTB that Americans assured her that they had "changed their practices" since 2014 and would work with allies to determine what had happened.
"We met today with the US Embassy [official] in Oslo to follow up on this", she said.
The US embassy is temporarily led by charge d'affaires Richard Riley.
The Danish public broadcaster DR reported on Sunday that the Nordic nation’s Defence Intelligence Service let the US National Security Agency tap into Danish underwater internet cables to eavesdrop on German Chancellor Angela Merkel and others. EU leaders have demanded explanations.