The British government said that the Kremlin was developing plans to install a pro-Russian leader in Ukraine—and had already chosen a potential candidate—as President Vladimir Putin weighs whether to order the Russian forces amassed on Ukraine’s border to attack, The New York Times reported.

The communiqué by the United Kingdom’s Foreign and Commonwealth Office, issued late at Saturday night in London, comes at a moment of high-stakes diplomacy between the Kremlin and the West. Russia has deployed more than 100,000 Russian troops on Ukraine’s borders that could, according to American officials, attack at any moment.

“The information being released today shines a light on the extent of Russian activity designed to subvert Ukraine, and is an insight into Kremlin thinking,” Liz Truss, Britain’s foreign secretary, said in a statement. “Russia must de-escalate, end its campaigns of aggression and disinformation, and pursue a path of diplomacy.”

These accusations from Britain provided few details about how Russia might go about imposing a new government on Ukraine, and the communiqué did not say whether such plans were contingent on an invasion by Russian troops. British officials familiar with the situation, who spoke on condition of anonymity, said the intent was both to head off the activation of such plans and to put Putin on notice that this plot had been exposed.

According to the British assessment, Russian planners were considering installing a former member of the Ukrainian Parliament named Yevgeniy Murayev as leader of a pro-Kremlin puppet government in Kyiv. Once a member of the Russian-backed Party of Regions, Murayev is now head of a political party called Nashi, part of a constellation of opposition parties opposed to Ukraine’s pro-Western parties.

But the Russian foreign ministry denied the British accusation.

“The spread of disinformation by the British foreign ministry is one more piece of evidence that NATO countries, led by the Anglo Saxons, are escalating tensions around Ukraine,” it said in a statement. “We call on the British foreign ministry to stop its prevocational activities.”