Blitzkrieg or Minor Incursion? Putin’s Choice Could Determine World Reaction.

“We believe President Putin has made the decision,” Mr. Blinken said on Sunday, “but until the tanks are actually rolling and the planes are flying, we will use every opportunity and every minute we have to see if diplomacy can still dissuade President Putin from carrying this forward.”

The White House released a statement on Sunday night that Mr. Biden had accepted “in principle” a summit with Mr. Putin after the meeting between Mr. Blinken and Mr. Lavrov, again specifying that it would only take place in the absence of an invasion.

The information passed to Mr. Biden from the intelligence agencies left unclear whether Mr. Putin’s orders would lead to a massive invasion or a more gradual approach that would give the Russian leader more opportunities to exploit fissures just beneath the surface in the Western alliance arrayed against him. He could, for example, test the proposition that Germany or Italy, the two Western European countries most dependent on Russian-provided gas, might falter in their resolve.

Those were the scenarios being discussed most intensely this weekend at the Munich Security Conference, the annual meeting of government ministers, corporate leaders and strategists, where attendees gamed out Mr. Putin’s choices.

“If he is intent on escalating, I don’t think it’s a sudden blitzkrieg to Kyiv and the ouster of the Zelensky government,” said Ian Bremmer, the president of the Eurasia Group, a geopolitical consulting firm. “It’s much more likely to look like a recognition of the independence of the breakaway territory” around Luhansk, in the east.

“You hope, if you are Putin, that leads to more skittishness of some of the NATO allies, less alignment with NATO, more opportunities for Russia to get what it wants without having to go full-scale into Ukraine,” Mr. Bremmer said.

A few weeks ago, some American officials shared that sentiment. Mr. Putin, they noted, presumably wanted to achieve his goal — a halt to Ukraine’s drift toward the West — as cheaply and with as few casualties as possible. All he sought was a friendly, pliable government like the one he has in Belarus, said one senior American official, who spoke on the condition of anonymity because of the continuing diplomatic efforts. The president of Belarus, Aleksandr G. Lukashenko, has tied the security of his country to the presence of the Russian military. (“They will be here as long as necessary,” said Mr. Lukashenko, who is considering inviting Russia to place its nuclear weapons back on Belarusian territory.)