President Joe Biden declared Tuesday that Russia's latest moves amounted to "the beginning of a Russian invasion of Ukraine," announced new sanctions and said he would send additional U.S. troops to the region.
The president said the sanctions would target large Russian banks, Russia's sovereign debt, and, starting Wednesday, the Russian elite and their relatives, and he threatened to add more if Russian President Vladimir Putin takes even more aggressive action.
"This is the beginning of a Russian invasion of Ukraine, as he indicated and asked permission to be able to do from his Duma," referring to the Russian parliament, Biden said in remarks from the White House.
He said, "if Russia goes further with this invasion, we stand prepared to go further as with sanctions."
"None of us, none of us should be fooled," the president said. "None of us will be fooled. There is no justification. Further Russian assault in Ukraine remains a severe threat in the days ahead."
Putin, in ordering Russian troops into two Russian-backed separatist regions in eastern Ukraine, was "setting up a rationale to take more territory by force," Biden said.
"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?" he said.
Calling the Russian moves "a flagrant violation of international law" and one that "demands a firm response from the international community," Biden said "full blocking sanctions" would be placed on two large Russian financial institutions and "comprehensive sanctions' on Russia's sovereign debt.
"That means we've cut off Russia's government from western financing. It can no longer raise money from the West and can not trade in its new debt on our markets or European markets either," he said.
Starting Wednesday, he said, "we'll also impose sanctions on Russia's elites and their family members. They share in the corrupt gains of the Kremlin policies and should share in the pain as well."
Biden also announced he would send more troops to the Baltics.
"Today, in response to Russia's admission that it will not withdraw its forces from Belarus, I have authorized the additional movements of U.S. forces and equipment already stationed in Europe, to strengthen our Baltic allies, Estonia, Latvia and Lithuania," he said.
Biden did not provide more details but called the deployments other than calling them "totally defensive moves on our part." He noted "we have no intention of fighting Russia" and said it was about sending "an unmistakable message" the U.S. "will defend every inch of NATO territory."
Several experts told ABC News that the new U.S. sanctions would have minimal impact on Russia's behavior and finances -- and that they stopped far short of the more severe sanctions that the White House had signaled it could eventually levy.
"This is an ante to say, 'This is the beginning of what we can do,'" said Julia Friedlander, a former Treasury Department official who is now a fellow at the Atlantic Council.
The Treasury Department said it would target two banks important to the Russian government and defense sector.
But Russia has anticipated sanctions, with significant foreign currency reserves and a sizable national wealth fund, experts said.
Andrew Lohsen, who worked as an officer and analyst at the Organization for Security and Co-operation in Europe's Ukraine mission, said that if the U.S. wanted to make a real impact, it should sanction Russia's largest banks where most Russians hold accounts: Gazprombank, VTB Bank and Sberbank.
"Those haven't been touched," Lohsen, a fellow at the Center for Strategic and International Studies, said. "There's obviously a belief that there's still some leverage that can be gained from holding those three banks in particular in reserve."
While the European Union and NATO have both said Russia had moved forces into Ukraine, Biden stopped short of saying whether Russia had done so, instead focusing on Russia recognizing the independence of two breakaway Ukrainian provinces already partially controlled by pro-Russian separatists.
His remarks followed nearly a daylong linguistic dance around how the U.S. would characterize and react to Putin's moves.
After for weeks saying the U.S. would impose "severe and swift" sanctions on Russia if it invaded Ukraine, the Biden administration has been grappling with whether Russia's decision to send troops across the border would trigger the most severe punishments it had prepared.
The U.S. on Monday imposed limited sanctions in response to Russia recognizing the regions' independence, and blasted Putin for ordering troops into those regions.
But as the White House stopped short of putting in place sanctions it said would make Russia an "international pariah," observers were left to parse what, in President Joe Biden's eyes, would actually prompt that.
"Russia will be held accountable if it invades," Biden said at a news conference on Jan. 19. "And it depends on what it does. It's one thing if it's a minor incursion and then we end up having a fight about what to do and not do, et cetera."
Within hours, his press secretary, Jen Psaki, clarified: "If any Russian military forces move across the Ukrainian border, that's a renewed invasion, and it will be met with a swift, severe, and united response from the United States and our allies."
The next day, Biden, too, added: "If any -- any -- assembled Russian units move across the Ukrainian border, that is an invasion" that "would be met with severe and coordinated economic response that I've discussed in detail with our allies."
And his top national security adviser, Jake Sullivan, said in a Feb. 6 interview with NBC News: "President Biden has spoken to the fact that if a Russian tank or a Russian troop moves across the border, that's an invasion" that would result in "severe economic consequences."
But with Putin so far ordering troops into regions where Russian operatives already operate -- albeit within Ukraine's internationally recognized borders -- it was unclear what, exactly, would trigger the larger sanctions.
"We think this is, yes, the beginning of an invasion, Russia's latest invasion, into Ukraine, and you already seeing the beginning of our response that we've said would be swift and severe," Jon Finer, the principal deputy U.S. national security adviser, said in an interview with CNN Tuesday.
"An invasion is an invasion, and that is what is underway," he said. "But Russia has been invading Ukraine since 2014."
Administration officials, though, had in the past suggested to reporters that sanctions would not come in a piecemeal fashion.
Psaki, though, said Monday that the sanctions the U.S. was announcing were "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."
The linguistic dance took place in Europe, as well, where the European Union's foreign policy chief, Josep Borrell, on Tuesday told reporters that "Russian troops are on Ukrainian soil" but that he wouldn't call Russia's actions "a fully-fledged invasion."
NATO's secretary-general, Jens Stoltenberg, also said Tuesday that there was evidence additional Russian forces had moved into Ukraine, and that Russia had moved from "covert attempts to destabilize Ukraine to overt military action."
After Russia's actions Monday, the U.S. and its allies began imposing a series of cascading sanctions.
The U.S. on Monday targeted people connected to the two separatist-controlled areas. On Tuesday, Germany took the major step of suspending the Nord Stream 2 gas pipeline from Russia; the U.K. imposed sanctions on three Russian oligarchs, five Russian banks and Russian parliamentarians; and the European Union put penalties on banks, decision-makers and lawmakers involved in the independence recognition and limits on Russia's ability to access EU financial markets and services.
"What's good is that there was unity," said Tom Graham, a former State Department and White House National Security official, now with the Council on Foreign Relations. "Everybody did something. They were coordinated."
But the moves -- particularly from the United States - stopped far short of the most severe sanctions the White House has threatened. It has warned it was preparing to restrict Russians' access to semiconductors; punish Russia's aerospace, defense and high-tech industries; cripple the country's largest financial institutions; and hit even Putin and those around him.
"If Russia invades Ukraine, it would become a pariah to the international community, it would become isolated from global financial markets, and it would be deprived of the most sophisticated technological inputs," the White House's top national security official crafting sanctions, Daleep Singh, said Friday.
Tuesday's sanctions -- from the U.S. and Europe -- "were hardly devastating at all," Graham said.
U.S. officials have for weeks been working to get European allies to act in unison on reacting to Russia. Biden and other top U.S. officials have repeatedly threatened "swift and severe consequences."
American officials have signaled that there is more agreement with other Western nations on what would happen if Russia carries out a full-scale invasion of Ukraine -- but that if Russia stops short and the world sees other scenarios play out -- like a partial invasion of eastern Ukraine, or solely recognizing the regions' independence, for example -- the kaleidoscope of possible penalties might not come into full harmony.
ABC News' Mary Bruce and Christine Theodorou contributed to this report.