NEW YORK, Feb 17 - A new Russian invasion of Ukraine appears imminent, possibly within “several days,” with signs pointing toward Moscow using a false pretext to send in troops amid alleged shelling in a contested region, President Joe Biden and some of his top aides said Thursday.

In a surprise appearance at the United Nations, Secretary of State Antony Blinken laid out the potential, “theatrical” steps American officials expect the Kremlin to take.

The U.S. officials’ warnings were the most dire to date in a conflict that has reached a fever pitch since Russian leader Vladimir Putin began amassing troops along the border with Ukraine last fall. Reports earlier this week from Russia indicated Putin may be pulling some troops back, but U.S. officials said Wednesday and Thursday that they believe Moscow has increased its troop presence to some 150,000 along the Ukrainian border with 7,000 new troops arriving in recent days.

Speaking of potential incursion, Biden on Thursday said his “sense is that it will happen within the next several days.” Other U.S. officials’ comments suggested a Russian attack could take place even sooner. Russia’s own announcements hinted that Putin was not happy with the direction of diplomatic efforts to solve the crisis, even as Moscow blamed Ukraine and the West for provocations and ignoring its security concerns.

The situation was so tense that American national security officials held multiple meetings overnight and U.S. Ambassador to the United Nations Linda Thomas-Greenfield asked Blinken to speak at a U.N. Security Council meeting on Thursday on his way to the Munich Security Conference.

The evidence on the ground is that Russia is moving toward an imminent invasion. This is a crucial moment,” Thomas-Greenfield told reporters Thursday morning.

Blinken went step-by-step to predict how Moscow would approach the situation, all part of an ongoing effort by the Biden administration to counter Russia’s disinformation and propaganda in as close to real time as possible.

First, Blinken said, Russia would come up with a pretext, possibly a “violent event” or an “outrageous accusation.”

“Second, in response to this manufactured provocation, the highest levels of the Russian government may theatrically convene emergency meetings to address the so-called crisis the government will introduce proclamations declaring that Russia must respond to defend citizens or ethnic Russians in Ukraine,” he said.

Once the attack starts, he added, “Russian missiles and bombs drop across Ukraine. Communications will be jammed. Cyberattacks will shut down key Ukrainian institutions. After that, Russian tanks and soldiers advance on key targets that have been mapped out in detailed plans. We believe these targets include Ukraine’s capital, Kyiv.”

Blinken said that he had written to his Russian counterpart, Sergey Lavrov, proposing that they meet next week in Europe. “We are also proposing meetings of the NATO-Russia Council and the OSCE Permanent Council,” he added. The goal is to pave the way for a “summit of key leaders, in the context of de-escalation, to reach understandings on our mutual security concerns.” (po/ez)