Washington(CNN) President Joe Biden described events now underway in Ukraine as "the beginning of a Russian invasion" as he unveiled tough new sanctions to punish Moscow on Tuesday.
He laid out what he called a "first tranche" of US sanctions against Russia for its moves, including on two large financial institutions, Russian sovereign debt and Russian elites and their family members. He said the moves would effectively "cut off Russia's government from Western finance."
Biden also announced he was moving additional troops and equipment to "strengthen" US allies in the Baltic nations on NATO's eastern flank, but made clear they would not be there to "fight Russia."
The President held out the possibility that diplomacy could still defuse the crisis, and said the US would remain open to talking with Russia and its partners to avert all-out war. "The United States and our allies and partners remain open to diplomacy, if it is serious," he said. "When all is said and done, we're going to judge Russia by its actions, not its words."
Still, Biden made plain his view that Putin was launching a bid to fundamentally redraw borders in Europe, violating international laws and putting pressure on the West to respond.
"Who in the Lord's name does Putin think gives him the right to declare new so-called countries on territory that belonged to his neighbors? This is a flagrant violation of international law and demands a firm response from the international community," Biden said.
Biden said Putin's remarks a day earlier were "setting up a rationale to take more territory by force, in my view."
Biden's description of a Russian invasion in Ukraine immediately ups the stakes for his response. He and other senior officials have vowed to impose severe economic consequences if Russian troops cross into Ukraine, including on members of Putin's inner-circle and Russian financial institutions.
The steps Biden announced Tuesday did not amount to the full scope of that response. Biden is reserving some of his toughest measures, hoping to use them should Putin wage the type of bloody and sustained attack US officials have been warning about for weeks.
Tuesday's sanctions are "only the sharp edge of the pain we can inflict," a senior US administration official said after Biden's remarks, suggesting the President is ready to go much further should an invasion of Ukraine escalate.
"This is the beginning of an invasion, and therefore this is the beginning of our response," the official said.
Biden pledged his administration was using "every tool at our disposal" to limit the effect of sanctions on domestic gas prices, acknowledging that Americans will likely see rising prices at the pump in the coming months.
"As I said last week, defending freedom will have costs, for us as well and here at home," Biden said. "We need to be honest about that. But as we do this, I'm going to take robust action to make sure the pain of our sanctions is targeted at the Russian economy, not ours."
The administration began describing events in eastern Ukraine as an "invasion" earlier Tuesday after assessing the situation on the ground there, according to administration officials.
The White House declined to provide specific intelligence that might further explain the shift in tone.
"We think this is, yes, the beginning of an invasion, Russia's latest invasion into Ukraine," US principal deputy national security adviser Jon Finer said in an interview on CNN's "New Day," adding the sanctions imposed Monday were the merely the "beginning" of the US response.
"An invasion is an invasion and that is what is underway," Finer said. "I am calling it an invasion."
Another top US official, Deputy Secretary of State Wendy Sherman, told the Organization for Security and Cooperation in Europe (OSCE) Russia's actions "are the beginning of the latest Russian invasion of Ukraine."
"They are utterly unprovoked and unjustified," Sherman said. "Moscow calls these troops 'peacekeepers,' but we all know this is a lie."
That was further than US officials were willing to go on Monday evening, and reflected the growing sense among Biden's team that a fuller assault on Ukrainian territory would begin shortly. Officials said continued signs of Russian aggression overnight led to a change in tone.
Still, Finer noted Russian troops have been operating in the two separatist regions since 2014, when Russia initiated an incursion into Ukraine, and suggested the latest steps taken by Moscow were an extension of that.
"I think 'latest' is important here," Finer said. "An invasion is an invasion, and that is what is underway, but Russia has been invading Ukraine since 2014."
There are substantial numbers of Russian troops close to the borders with the newly recognized republics. But CNN has not seen social media video nor satellite imagery showing newly arrived Russian units inside either of the separatist-held regions of Luhansk and Donetsk.
The US continues to assess it is still possible Putin moves ahead with a fuller invasion, and Western officials are being vigilant for additional indicators, according to two US officials briefed on the assessment. There may be window of dry weather, making it easier for the Russians to move heavy equipment, along with cloud cover that could help obscure movements. Still, one of the officials acknowledged "we don't know what his next move will be."
The developments were unfolding as Putin ordered Russian troops into two separatist-held regions of Eastern Ukraine after declaring them independent. Biden, responding in the hours after Putin signed the orders, issued a narrow set of restrictions limiting financial activity in the two regions.
As he was readying Tuesday's announcement, the US was coordinating with allies in Europe in the hopes of averting a full-scale war. Earlier, Germany said it was halting certification of the Nord Stream 2 gas pipeline, a step US leaders had been pressing for as the crisis heats up.
"With regard to the latest developments, we need to reassess the situation also with regard to Nord Stream 2. It sounds very technocratic but it is the necessary administrative step in order to stop certification of the pipeline," Chancellor Olaf Scholz said in Berlin.
The 750-mile pipeline was completed in September but has not yet received final certification from German regulators. Without that, natural gas cannot flow through the Baltic Sea pipeline from Russia to Germany.
The United Kingdom said Tuesday it was slapping sanctions on five Russian banks and three wealthy individuals following Putin's decision to recognize two separatist republics.
Prime Minister Boris Johnson announced the sanctions in a statement to the UK parliament on Tuesday, saying Putin was "establishing the pretext for full scale invasion" of Ukraine.
The European Union was also preparing a first package of sanctions against Russia on Tuesday, its top official said in a joint statement on Tuesday. The package will contain proposals targeting those involved in the "illegal decision" to recognize two separatist regions in eastern Ukraine and banks that are "financing Russian military and other operations in those territories." Those sanctions will also limit Russian state and government to access the EU's capital and financial markets.
This story has been updated to reflect additional developments on Tuesday.