(CNN) Russian President Vladimir Putin's move to recognize breakaway eastern Ukrainian territories as independent could be the opening phase of a larger potential military operation targeting Ukraine, nearly a dozen US and western officials told CNN.
"This is Potemkin politics," a senior administration official told reporters on Monday. "President Putin is accelerating the very conflict that he's created."
The US and western officials said Putin's decision to sign the decrees, which proclaim that the Russia-backed Donetsk People's Republic (DNR) and Luhansk People's Republic (LNR) are independent territories, has given Putin the justification he wanted to send in Russian forces and potentially wage a broader assault on Ukraine in the name of protecting the separatist regions.
US Ambassador to the United Nations Linda Thomas-Greenfield called the announcement a pretext to an invasion. "Russia's announcement is nothing more than theater, apparently designed to create a pretext for a further invasion of Ukraine," she said in a statement.
The US expects Russian troops could move into the Donbas region of Ukraine as soon as Monday evening or Tuesday, after Putin recognized the two pro-Moscow territories as independent, a senior US official familiar with the latest intelligence told CNN. The US is still seeing preparations for a potential broad invasion including loading amphibious ships and loading equipment for airborne units.
The Kremlin announced on Monday evening that Russia would be sending what it called "peacekeeping" forces into the breakaway territories, confirming many officials' worst fears.
"That's your invasion," said one European diplomat. "If we don't act on this as we have said we would in case of a further invasion, we will have seriously undermined our credibility," the diplomat said.
Former Director of National Intelligence James Clapper weighed in on the move from Russia, telling CNN's Wolf Blitzer Monday evening that "when any Russian troops march into any part of Ukraine under any pretense regardless of what it's called that, to me, walks like a duck, quacks like a duck, it's an invasion."
Still, in a call with reporters the senior administration official suggested that the mere movement of what Russia is calling "peacekeeping" forces into eastern Ukraine would not itself trigger the full sanctions package the Biden administration has threatened in the event of a Russian invasion, noting that "there have been Russian forces present in these areas" since 2014.
"So we're going to be looking very closely at what they do over the coming hours and days and our response will be measured, according, again, to their actions," the official said. The official said "it now looks like Russia will be operating openly in that region, and we will be responding accordingly."
The official would not identify what line Russian troops would have to cross in Eastern Ukraine to be considered a new invasion.
The White House said on Monday that Biden would impose new financial restrictions on the breakaway republics, and the senior administration official told reporters that more actions would be announced on Tuesday. But some officials say the penalties do not go far enough -- especially considering Biden's claim last month that if "any assembled Russian units move across the Ukrainian border, that is an invasion," which would be met with "severe and coordinated economic response."
Putin formally signed the decree and ordered the forces in following a lengthy speech in which he called the situation in Ukraine's Donbas region "critical," and suggested that Ukraine was planning an attack on Russia. "The US and NATO shamelessly turned Ukraine into a theater of potential military action against Russia," Putin said in his remarks, which ran nearly an hour.
"We're now in a whole new era," said one western diplomat. "This kills Minsk. It's not clear where we go from here. It's a very dangerous time because we don't know what Putin will do next."
The Minsk Protocol is a framework for peace in eastern Ukraine that the US and its allies have been urging Russia to implement and abide by since 2015, when the agreement was first drawn up amid bloody clashes between Ukraine and pro-Russian separatists in the Donbas.
The officials said the US had been expecting that Putin would make a move to recognize the breakaway republics, as he has steadily been massing more forces near Ukraine's borders.
"We knew this was going to happen," said one US official, adding that "this is exactly what we have been predicting -- that he would find a pretext to justify further action."
That sentiment was echoed by White House press secretary Jen Psaki on Monday.
"We have anticipated a move like this from Russia and are ready to respond immediately," Psaki said in a statement, in which she also outlined the new executive order Biden will sign imposing financial restrictions on the separatist territories.
Putin's decision has put the US and its allies in a tricky position with regard to imposing consequences, several of the officials said. While the Biden administration will impose a cost on Putin for his recognition of the breakaway republics, the west also wants to maintain the threat of the most aggressive options as a deterrent to a full-scale invasion.
"To be clear: these measures are separate from and would be in addition to the swift and severe economic measures we have been preparing in coordination with Allies and partners should Russia further invade Ukraine," Psaki said in her statement.
Still, US and western officials said they hoped stronger sanctions would come -- and soon.
"I hope it is just an opening salvo," another European diplomat said of the sanctions announced by the White House on Monday in response to Putin's recognition of Luhansk and Donetsk. "I expect a punch, not finger-wagging," the diplomat added.
A European defense official, meanwhile, said that Putin's recognition of the breakaway republics is likely not his final goal.
"It will be the opening of the offensive, not a 'try and see what happens,'" the officials said. "If he goes for war, he will have to get his objectives fast and start preparing the 'peace' negotiations with the West."