Director of the US Central Intelligence Agency, William Burns, visited Ukraine in early October and met with President Volodymyr Zelenskiy and other officials.
Two informed sources told CNN.
"While there, he reaffirmed the commitment of the US to support Ukraine in its fight against Russian aggression, including through continued intelligence sharing," one of the sources said.
CNN spokespeople declined to provide more details about Burns' trip, which has not been officially reported.
The head of the CIA visited Ukraine amid growing concern in the US that Russia might resort to using nuclear weapons.
Publicly, the American side claims that they see no evidence that Russia is preparing such a step, but CNN interlocutors familiar with the intelligence warn that the risk of a nuclear strike by the Russian Federation is perhaps the highest since the beginning of a full-scale war.
Fears about the possible use of Russian nuclear weapons in Ukraine have increased since Moscow began to publicly talk about the alleged preparation of a provocation by Kyiv using a "dirty bomb". Both Ukraine and the West resolutely rejected these accusations.
As reported, against the backdrop of Russia's more active rhetoric about Ukraine's alleged preparation of a "dirty bomb" provocation, the United States does not see any new signs of Russia's preparations for a nuclear strike.