Whatever Mr. Putin’s intentions, American officials say they are rallying European allies for coordinated sanctions that would snap into place as soon as military action began. It is not clear, however, that the threat of such penalties would impress Mr. Putin, who has noted that Russia has lived with Western sanctions for years.
American and European officials are also continuing to monitor cyberattacks and disinformation campaigns that they say may be preparing the battlefield for any action. The senior administration official noted that such action has “often been done in advance these of sorts of incursions in the past.” The disinformation campaign has attempted to create a narrative that Ukraine is the country provoking a conflict.
In another sign of Western engagement, Valery V. Gerasimov, Russia’s top military commander, spoke with his British counterpart, Sir Tony Radakin, on Thursday, and with Mark A. Milley, the chairman of the Joint Chiefs of Staff, on Wednesday. But in a move underscoring the continuing tensions, Russia on Thursday announced snap paratrooper exercises in and around Crimea, the Black Sea peninsula annexed from Ukraine in 2014.
Understand the Escalating Tensions Over Ukraine
Ominous warnings. Russia called the strike a destabilizing act that violated the cease-fire agreement, raising fears of a new intervention in Ukraine that could draw the United States and Europe into a new phase of the conflict.
The Kremlin’s position. President Vladimir V. Putin of Russia, who has increasingly portrayed NATO’s eastward expansion as an existential threat to his country, said that Moscow’s military buildup was a response to Ukraine’s deepening partnership with the alliance.
In his assertions about bringing missiles “to our home’’ Mr. Putin appeared to be referring to missile-defense systems in Poland and Romania. He has alleged that the systems can be used for offensive purposes and could soon be installed in Ukraine; Western officials deny those claims, noting that missile interceptors are, by definition, used only to repel incoming attacks.
American officials say removing missile defenses from NATO countries would undercut European security. They also say they will continue to arm Ukraine with defensive weaponry, including Javelin missiles used against Russian tanks. But because Ukraine is not a NATO member,NATO does not keep antimissile defenses or nuclear weapons there.
The freewheeling news conference on Thursday was a stark demonstration of the Kremlin’s image-making of Mr. Putin as an all-around expert and benevolent leader — a “good czar” keeping local officials in check while steering the world’s biggest country. The lengthy session, meant to display Mr. Putin’s authority and stamina, included a range of questions on far-flung topics including “cancel culture’’ and Father Frost, Russia’s version of Santa Claus.