The White House hasdenied any involvement in an alleged drone attack on the Kremlin, after Russian spokesman Dmitry Peskov accused Washington of guiding Ukraine to launch the assault.
"We had nothing to do with this," said John Kirby, spokesperson for the White House National Security Council, on MSNBC.
"Peskov is just lying there, pure and simple," he added.
Russia alleges that Ukraine carried out a "terrorist attack" overnight Tuesday into Wednesday with two drones, aiming to kill President Vladimir Putin, a charge which Kyiv has denied.
Throughout its more than year-long offensive in Ukraine, Moscow has maintained that Kyiv is taking orders from Washington -- accusing the West of leading a war against Russia by proxy.
Peskov, Putin's longtime press secretary, said earlier Wednesday that "decisions on such attacks are not made in Kyiv, but in Washington."
"Kyiv only does what it is told to do," he added.
Kirby reiterated to CNN later that Washington "had no role in it whatsoever," and that the White House was still seeking clarification on the incident.
"We honestly just don't know what happened here," he said.
The incident at the Kremlin comes amid several other recent explosions and train derailments on Russian and occupied Ukrainian territory, with Moscow pointing the finger at Kyiv.
Kirby reiterated in his interview to MSNBC on Wednesday that Washington does not support or condone attacks by Ukraine outside its borders.
"We've been clear with them publicly and we've been clear with them privately that we do not encourage nor do we enable them to strike outside Ukraine," he said.
Asked later on CNN if Washington viewed Putin as a legitimate military target, Kirby said: "We don't favor -- we don't endorse strikes on individual leaders."
The United States has led a coalition of Western nations in arming the Ukrainian military, steadily giving it more advanced weaponry and defense systems requested by President Vladimir Zelensky.
On Wednesday, the White House announced a new $300 million military aid package, featuring a slew of ammunition, bringing total US security assistance to Ukraine to $35.7 billion.
The White House says the package will help fulfill Ukraine's requests ahead of a planned counteroffensive, which it has been preparing for months.
Zelensky now has "about 98 percent of everything his forces say they need to be able to conduct offensive operations in the spring and the weeks and months ahead," Kirby told CNN.
EU warns Moscow not to use drone 'attack' to escalate war
Meanwhile, EU foreign policy chief Josep Borrell warned Moscow on Thursday to not use the alleged drone attack to escalate its war in Ukraine.
"We call on Russia not to use this alleged attack as an excuse to continue the escalation of the war," Borrell told journalists as he went in to attend an EU ministers meeting in Brussels.
"This is what worries us: this can be used to justify more conscription of people, more soldiers, more attacks on Ukraine."
Borrell said he had heard Ukrainian President Volodymyr Zelensky deny that Ukraine was behind the attack, which Russia said occurred in the early hours of Wednesday.
Moscow said anti-aircraft units shot down the drones, claiming the alleged attack was an assassination attempt on Russian President Vladimir Putin, who does not sleep in the Kremlin.
Borrell said: "I listened to President Zelensky; President Zelensky said clearly Ukraine is not involved in the attacks, that they are defending their country, but they are fighting on their soil, that they are not attacking Russian soil."
Former Russian president Dmitry Medvedev, who on Wednesday called for the "physical elimination" of Zelensky over the purported drone attack, on Thursday criticised Borrell as "an impudent old fool".
Referring to Borrell's warning against an escalation, Medvedev tweeted in English that the alleged attack "is exactly to the escalation of the conflict it will lead".
"This is just what Washington and many dumbheads in Brussels want," Medvedev said.