There is no indication that Russian President Vladimir Putin will stop the aggression toward Ukraine despite recent talks with world leaders, a former U.S. ambassador to Russia said.
"There's no indication at all that Putin has stopped his march towards war, his preparedness towards war," said Michael McFaul, who is now director at the Freeman Spogli Institute for International Studies.
"Every indication is that he continues to build up his forces on all borders and from the water, against Ukraine," he told CNBC's "Squawk Box Asia" on Monday.
Russian troops have amassed along the country's border with Ukraine for months, sparking fears that Moscow may invade Ukraine in a repeat of the 2014 annexation of Crimea. Russia has denied those allegations.
White House national security advisor Jake Sullivan on Sunday said the Kremlin has accelerated its military buildup in recent days.
The United States previously said Russia may fabricate an attack by Ukraine as a pretext for invading its neighbor.
McFaul said false flag attacks are a "good tactic" by Russia and are not new. He said the warnings from the U.S. are "credible," though Moscow has denied the allegations.
"I admire how the Biden administration is leaning into this and declassifying information that normally is pretty hard to declassify. It suggests to me that it's credible," he said.
Uncertainty
However, McFaul said no one knows what will happen next in Russia-Ukraine tensions or how Moscow will respond to sanctions from the U.S. and the West.
"I don't think anybody knows. I think there's a lot of uncertainty right now," he said.
That's in part because the Russian leader is "isolated," he said.
"Putin is so isolated, even in his own country. He rarely talks to advisors," said McFaul, adding that "we don't have a lot of fidelity on what he's thinking."
— CNBC's Amanda Macias contributed to this report.