US and Western officials caught off guard by Prigozhin's escalation in Russia

US and Western officials are being careful not to weigh in on the events unfolding in Russia because of how Russian President Vladimir Putin could weaponize any perceived involvement by the west in the escalating crisis, sources familiar with the administration's thinking told CNN.

Officials across the administration convened emergency meetings on Friday night to assess the events, which unfolded so quickly that they caught US and European officials off guard, the sources said. Yevgeny Prigozhin, chief of the private Wagner military group, vowed Friday to retaliate against Russian military leadership over an alleged strike on a Wagner military camp and has since claimed control of military facilities in two Russian cities.

US Secretary of State Antony Blinken's office confirmed Saturday that he spoke with officials from Canada, France, Germany, Italy, Japan, United Kingdom, and the European Union.

During the discussion, "Secretary Blinken reiterated that support by the United States for Ukraine will not change," said State Department spokesperson Matthew Miller, adding that the US "will stay in close coordination" with Western officials.

Britain, meanwhile, held a meeting of its emergency government task force to discuss the unfolding events, a UK Foreign, Commonwealth and Development Office spokesperson told CNN.

As Russia's invasion of Ukraine stalled earlier this year, US officials determined last year that there was an internal power struggle underway between the Wagner group and the Russian government, CNN previously reported. However, US and European intelligence officials did not predict that Prigozhin would move to storm the Russian region of Rostov with his forces, according to sources familiar with the intelligence.

"It's so hard to tell how much was talk and how much was real," one of the sources told CNN. "The tension had been building for so long without anything actually happening."

On Friday, Prigozhin, once an ally of Putin, accused Russia's military leadership of killing a "huge amount" of his mercenary forces in a strike on a Wagner camp -- which the Russian Ministry of Defense has denied -- and vowed to retaliate. Prigozhin also claimed that Moscow invaded Ukraine under false pretenses devised by the Russian Ministry of Defense, and that Russia is actually losing ground on the battlefield.

After swiftly claiming control of military facilities in two Russian cities, Prigozhin has warned that his troops would head to Moscow. In response, Putin has vowed to punish the "armed uprising."

A European intelligence official told CNN that the "temperature had obviously been building," but few could have predicted what Prigozhin was planning. The official said the West will be watching how this plays out in the next 24 to 48 hours, after which supply shortages will likely start kicking in for Wagner forces.

It is not clear to US or European officials how far in advance Prigozhin was planning the rebellion. One source familiar with Western intelligence said it appeared that it must have taken at least several days to organize. Another source, however, noted that Rostov is very close to the frontlines in Ukraine so it may not have required much forethought.

Ukrainian President Volodymyr Zelensky said Saturday that this conflict has exposed Russia's "weakness," with a Ukrainian defense spokesperson calling it a "sign of the collapse of the Putin regime."

"Russia's weakness is obvious. Full-scale weakness," Zelensky said in a tweet. "And the longer Russia keeps its troops and mercenaries on our land, the more chaos, pain, and problems it will have for itself later."