Russia was informed in advance about US President Joe Biden's visit to Kiev, according to US National Security Advisor Jake Sullivan.
"Because of the sensitive nature of those communications I won't get into how they responded or what the precise nature of our message was, but I can confirm that we provided that notification," Sullivan said on a phone call with journalists.
The information had been provided a few hours ahead of Biden's trip.
Washington has so far not provided details on how Biden reached Kiev. Due to the war, state guests have generally been travelling to the Ukrainian capital by train.
Biden's delegation said details on the itinerary would be provided later, once the information had been released by the security services.
Biden travelled on to Poland after commemorating the first anniversary of the war, which began with Russia's full-scale invasion on February 24, 2022.
