US officials alleged Thursday that Russia has been preparing to “fabricate a pretext for an invasion” of Ukraine by creating “a very graphic propaganda video” that would depict a fake attack by Ukraine against Russia. The US’ disclosure of the alleged plot is the latest in a series of revelations designed to blunt the impact of any pretext Russia may use to invade Ukraine, and comes after US officials warned that Moscow could use a false flag operation to justify such an invasion. Russia has continued building up forces and military equipment along Ukraine’s borders, despite diplomatic efforts by the US and allies to de-escalate the situation. Speaking at a Pentagon briefing Thursday, press secretary John Kirby said that the US believes the Russian government “is planning to stage a fake attack by Ukrainian military or intelligence forces against Russian sovereign territory or against Russian-speaking people” in order to create false rationale for an invasion. “As part of this fake attack, we believe that Russia would produce a very graphic propaganda video which would include corpses and actors that would be depicting mourners and images of destroyed locations, as well as military equipment at the hands of Ukraine or the West, even to the point where some of this equipment would be made to look like it was Western supplied … to Ukraine equipment,” Kirby said. Russian Ambassador to the European Union Vladimir Chizhov told CNN Thursday that Moscow is not planning any false flag operations to invade Ukraine. Price, the State Department spokesperson, declined to provide evidence of the US’ claim when repeatedly pressed during a press briefing Thursday. He said the information he was sharing about the alleged plans was based on declassified US intelligence, which he said the US shares with the public “only when we’re confident in that information.” “We are trying to deter the Russians from moving forward with this type of activity. That is why we are making it public today. If the Russians don’t go forward with this, that is not ipso facto an indication that they never had plans to do so,” Price claimed. The Washington Post first reported the story. Also on Thursday, US Secretary of State Antony Blinken signed a new defense cooperation agreement between the US and Slovakia at the State Department, a move that is likely to anger Moscow. Blinken made the announcement alongside top Slovak officials, Foreign Minister Ivan Korčok and Defense Minister Jaroslav Naď, who pointed to European security being at stake due to Russian aggressions. UK Foreign Secretary Liz Truss said Thursday that the US disclosure about the alleged Russian false flag plans “is clear and shocking evidence of Russia’s unprovoked aggression and underhand activity to destabilise Ukraine.” “This bellicose intent towards a sovereign, democratic country is completely unacceptable and we condemn it in the strongest possible terms,” she said in a statement. ‘I’m not going to spell out what is in our possession’ Price would not say if the US had seen an actual video, saying, “the fact that we are able to go into such great detail, obviously I’m not going to spell out what is in our possession, but I will leave it to you, I will leave that to your judgment.” A source familiar said the US does not have the video nor does it have evidence that it has actually been made. A senior administration official told CNN that the US believes Russia has already recruited actors to be involved in the alleged fake attack. The official said the video could include images of Bayraktar drones, which NATO ally Turkey has provided to Ukraine, “as a means to implicate NATO in the attack.” This official said the video would “be released to underscore a threat to Russia’s security and to underpin military operations,” and “could provide Putin the spark he needs to initiate and justify military operations against Ukraine.”’ “It shows the level of cynicism, frankly, that is on the other side of this conflict,” deputy national security adviser Jon Finer told MSNBC on Thursday. “We’re not saying definitively this is what they’re going to do. We are saying that this is an option under consideration, and that they have used these sorts of pretext in the past to justify military action.” Finer said the US is making the accusation public in order to “make it much more difficult for [Russia] after the fact to claim that they had to do whatever they decided to do.” Speaking to CNN’s Bianca Nobilo Thursday, US Ambassador to NATO Julie Smith said that false flag operations are part of Russia’s playbook. “We saw this in 2014, we’ve seen other efforts for them to use these types of tactics over the last 10 years,” Smith said. “And so what you heard today is just another piece of information where Russia is clearly laying the groundwork to destabilize Ukraine from within and find a pretext to take action using the military forces that it’s built up around the border.” Last month, CNN first reported that the US had information indicating Russia had prepositioned a group of operatives to conduct a false-flag operation in eastern Ukraine in an attempt to create a pretext for an invasion. The senior administration official also said on Thursday that if Russia decides to change how it views separatist territories in eastern Ukraine—for example, if it decides to view them as independent rather than as part of Ukraine following a legal change by Russia’s parliament now under consideration—then Moscow “could claim that the push for independence led Ukraine to ‘attack’” pro-Russian forces in the east. “To build the case for independence, Russian politicians are advancing this legislation on the false basis that Ukraine is preparing to forcibly retake this territory and that Kyiv has systematically denied local residents their basic rights,” the official said. “In line with its previous interventions, Russia would portray its actions as defending ethnic Russians and coming at the request of a sovereign government for assistance.” This story has been updated with additional details.