US officials have picked up chatter amongst Ukrainian officials blaming each other for a drone attack on the Kremlin earlier this month, contributing to a US assessment that a Ukrainian group may have been responsible, sources familiar with the intelligence told CNN.
The intercepts include some members of Ukraine's military and intelligence bureaucracy speculating that Ukrainian special operations forces conducted the operation.
The chatter, combined with other intercepted communications of Russian officials blaming Ukraine for the attack and wondering how it happened, has led US officials to consider the possibility that a Ukrainian group was behind the incident on May 3. On that morning, two drones flew up toward the Kremlin's Senate Palace and struck the top of the building.
However, the US has not been able to reach a definitive conclusion on who was responsible and only assesses with low confidence that a Ukrainian group may have been behind the incident, officials said. US officials also still believe it is unlikely that senior Ukrainian government officials, including Ukrainian President Volodymyr Zelensky, ordered the attack or knew about it beforehand.
Recent US intelligence reports have assessed that Russian officials have speculated privately, as they have publicly, that Ukraine was behind the attack, leading officials to believe that the incident was likely not a state-sponsored false-flag operation intended to give Russia a pretext to further escalate its war on Ukraine.
The Kremlin has also made some internal security changes in response to the attack, one source familiar with the intelligence said, declining to go into detail. Kremlin spokesperson Dmitry Peskov said publicly following the episode that the city's air defenses would be tightened.
The drones that hit the Kremlin appeared small, with a relatively light payload, which is probably why they didn't trigger Russian air defenses, sources told CNN. It is unclear whether they would have had sufficient range to be flown from Ukraine to Moscow.
Zelensky has denied Ukraine was behind the attack
Zelensky speculated earlier this month that the attack could have been a false flag operation, and denied his country was behind it.
"Russia has no victories to report," he told reporters while in Helsinki, Finland, earlier this month. "Because of that, [Russian President Vladimir Putin] has to do some unexpected moves like surprise drone attacks."
Moscow launched a wave of missiles at Kyiv following the incident, using drones that read "for Moscow" and "for the Kremlin," the Ukrainian military said.
"We didn't attack Putin," Zelensky added. "We leave it to the tribunal."
US officials do not believe it was an attempt to assassinate Putin. It is widely known that Putin does not spend a lot of time at the Kremlin, and he was not in the building at the time of the incident, Peskov has said.
There are still a number of possibilities that US officials have not ruled out, including that non-state Ukrainian or Russian actors inside Russia carried out the operation. That could include Russians sympathetic to Putin hoping to shore up support for him.
A spokesperson for Ukraine's defense intelligence agency referred CNN to Zelensky's comments in Helsinki.
'The Ukrainians are defending themselves'
It is not the first time the US has observed Ukrainian officials pointing the finger at each other following a mysterious attack against Russian targets, like the car bombing that killed Darya Dugina and the suspected truck bombing against the Kerch Bridge that connects Russia with Crimea, sources said.
The US also has intelligence that Ukraine has considered attacking Russia before. Classified Pentagon documents leaked online earlier this year revealed that the CIA urged Ukraine's military intelligence chief to "postpone" attacks on Russia on the anniversary of its invasion of Ukraine.
Another US intelligence report, which is sourced to signals intelligence, says that Zelensky in late February "suggested striking Russian deployment locations in Russia's Rostov Oblast" using unmanned aerial vehicles, since Ukraine does not have long-range weapons capable of reaching that far.
US officials have said consistently that they do not encourage Ukraine to launch cross-border attacks into Russia.
On a visit to Washington earlier this month, British Foreign Secretary James Cleverly claimed there was no new information about who conducted the attack but added that broadly speaking, "the Ukrainians are defending themselves."
"They need to defend themselves in a way that is effective," Cleverly said in response to a question from CNN. "They are the injured party in this, we should never lose sight of that. And in order to effectively defend themselves they do have to respond through the use of force. But always make sure that it's thoughtful, proportional and is supportive of their wider aims rather than in any way counterproductive."