Tensions between Russia and Ukraine escalated dramatically on Monday, with Russian President Vladimir Putin taking steps many saw as the groundwork for a military invasion of the country of more than 40 million people.
The Biden administration and its allies have for weeks pursued a diplomatic off-ramp to avoid a Russian invasion that could trigger war in Europe.
But the window appeared to close on Monday when Putin signed decrees recognizing as independent the so-called Donetsk People's Republic and Luhansk People's Republic, two regions of Ukraine's Donbas where Russian-backed separatists have been fighting Ukrainian forces for years.
Within hours, the Russian leader had directed the Russian military to conduct operations in those regions. Experts warned doing so could preview the Russian military launching full-scale operations in Ukrainian territory and set the stage for a further invasion.
"It's been like a building crescendo," Rose Gottemoeller, former Deputy Secretary General of NATO, told The Hill in an interview.
In hourlong remarks leading up to the recognition of the two regions as independent, Putin undertook what Western experts said was a rewriting of history that questioned the independence of Ukraine and portrayed the nation as historically and culturally Russian. He claimed Ukraine is being used by the West and took aim at the government of Ukrainian President Volodymyr Zelensky.
"This was a speech to the Russian people to justify war," a senior Biden administration official told reporters on Monday.
"We'll continue to pursue diplomacy until the tanks roll, but we are under no illusion about what is likely to come next," the official added.
U.S. Ambassador to the Organization for Security and Cooperation in Europe (OSCE), Michael Carpenter, called Putin's actions on Monday as setting up "a full-scale Russian war against Ukraine."
"Despite what Russia tries to allege, the cold hard truth is that Russia is right now trying to create a pretext for military action," Carpenter said in a statement delivered to the OSCE in Vienna.
Shortly after Putin's remarks Biden signed an executive order barring U.S. investments, trade and financing from flowing into the Donetsk and Luhansk regions and granting him the authority to impose sanctions on individuals operating in the regions.
The senior administration official indicated Monday more sanctions would likely be forthcoming on Tuesday, without offering any details. The European Union has also pledged to impose sanctions related to Putin's decision.
The White House has for weeks pledged to levy punishing economic sanctions against Russia should it launch a renewed military invasion of Ukraine, and pressure to do so likely will only grow after Monday's developments.
The senior administration official wouldn't directly answer questions about what would constitute a renewed Russian invasion of Ukraine, saying only that the U.S. would assess the steps Russia takes in the hours and days ahead and respond accordingly.
"We are going to observe and assess what Russia does in the hours ahead and overnight," the official said. "We are going to respond to any actions that Russia takes in a way that we believe is appropriate to the action."
At one point, the official noted that Russia has had military forces in the Donbas for eight years, but suggested that forces would be operating more overtly under Putin's order Monday.
Announcements of U.S. sanctions were coupled with U.S. Ambassador to the United Nations Linda Thomas-Greenfield saying she supported Ukraine's demand for the U.N. Security Council to hold an emergency meeting on Russia's threats against Ukraine.
Such a meeting would mark the third time in less than a month the Security Council would focus on the crisis with Russia and would take place while Russia holds the rotating presidency of the Security Council for the month of February.
"Every U.N. Member State has a stake in what comes next," Thomas-Greenfield said in a statement. "Russia's actions threaten the international order that, since World War II, has stood for the principle that one country cannot unilaterally redraw another country's borders. This principle is enshrined in the UN Charter which all Member States pledge to uphold."
The senior administration official on Monday said the U.S. sees value in holding another Security Council meeting as forcing Russia to "answer for the actions they took today" in the "foremost international body charged with maintaining peace and stability in the world."
The White House had signaled as late as Sunday night it was leaving the door open to diplomacy, even as its own officials had warned hours earlier of the likelihood of a violent and devastating invasion of Ukraine.
Press secretary Jen Psaki said Biden had agreed "in principle" to meet with Putin, as long as Russia did not invade Ukraine in the interim. But with Monday's actions by Moscow, such a meeting appeared off the table.
"Our strong sense, based on everything we are seeing on the ground in the areas around the Ukraine to the north, to the east, to the south, is that Russia is continuing to prepare for military action that could take place in the coming hours or days," the senior Biden administration official said.
Secretary of State Antony Blinken is scheduled to meet with Russian Foreign Minister Sergey Lavrov in Europe on Thursday. Lavrov seemed to indicate earlier on Monday that he would meet with the secretary, but the Biden administration appears to be discussing whether the meeting should proceed given Russia's latest actions.
David Kramer, who spent three years as deputy assistant secretary of State for European and Eurasian affairs during the George W. Bush administration, warned Russia's next moves could take a variety of forms. Moscow could launch major cyberattacks, seek to disrupt a pipeline that runs through Ukraine or send its military further into Ukrainian territory.
"There is a lot at stake here," said Kramer, who serves as an advisory board member to the foreign policy-focused Vandenberg Coalition. "But to do nothing in response to the latest forcible takeover of territory by Russia since World War II is not a tenable position because Putin's appetite will only grow."