WASHINGTON -- The buildup of Russian troops near Ukraine has left U.S. officials perplexed, muddying the Biden administration's response.
Some Republican lawmakers have been pressing the U.S. to step up military support for Ukraine. But that risks turning what may be mere muscle-flexing by Russian President Vladimir Putin into a full-blown confrontation that only adds to the peril for Ukraine and could trigger an energy crisis in Europe.
But a weak U.S. response carries its own risks. It could embolden Putin to take more aggressive steps against Ukraine as fears grow he could try to seize more of its territory. And it could cause more political damage for President Joe Biden at a time his popularity is dropping.
Knowing how to strike the right balance would be easier if the U.S. had a better understanding of what Putin was trying to accomplish. But top officials admit they don't know.
"We're not sure exactly what Mr. Putin is up to," Defense Secretary Lloyd Austin said Wednesday.
A week earlier, Secretary of State Antony Blinken said, "We don't have clarity into Moscow's intentions, but we do know its playbook."
Rep. Mike Quigley, D-Ill., said better understanding Putin's intentions was critical "to avoid the mistakes that have started great wars."
Any U.S. response must be calibrated to avoid being "an appeaser or a provocateur," said Quigley, a member of the House Intelligence Committee.
"This is a tough, tough area to try to gain information," he said. "It's a challenge that's as tough or tougher than it's ever been. It has a pretty serious impact on our ability to make the correct decisions."
Russia seized Ukraine's Crimean Peninsula in 2014 and an ongoing conflict in eastern Ukraine between Kyiv and Russian-backed rebels in the region known as Donbas has left an estimated 14,000 people dead. Now, Ukraine says an estimated 90,000 Russian troops have massed near the border.
The buildup could be a prelude to another Russian invasion. Speaking to Ukraine's foreign minister this month, Blinken said Putin's "playbook" was for Russia to build up forces near the border and then invade, "claiming falsely that it was provoked."
NATO Secretary-General Jens Stoltenberg said Friday that the alliance is seeing an "unusual concentration" of Russian forces along Ukraine's border, warning that the same type of forces was used by Moscow in the past to intervene in neighboring countries.
Though U.S. officials don't believe an invasion is imminent, Putin also has ramped up his dismissal of an independent Ukraine. A lengthy essay the Kremlin published in July asserts that Ukrainians and Russians are "one people" and the "true sovereignty of Ukraine is possible only in partnership with Russia."
But the moves could also be saber-rattling to prevent Ukraine from growing closer to the West or being admitted into the North Atlantic Treaty Organization, which Putin strongly opposes. It's not clear if Russia would risk invading Ukraine, setting off a far more difficult war, or want to occupy hostile territory.
Speaking Thursday, Putin said, "It should be taken into consideration that Western partners are exacerbating the situation by supplying lethal modern arms to Kyiv and carrying out provocative military maneuvers in the Black Sea -- and not only in the Black Sea but also in other regions close to our borders."
The White House said it hopes to de-escalate tensions.
"As we have made clear in the past, escalatory or aggressive actions by Russia would be of great concern to the United States," a spokesperson for the National Security Council said in a statement.
There has been a flurry of diplomacy in recent weeks.
U.S. leaders have met with their Russian and Ukrainian counterparts, including a visit by CIA Director William Burns to Moscow during which he spoke to Putin by phone. Germany and France have issued a joint statement affirming support for Ukraine.
Ultimately, the U.S. has few good apparent options to stop Putin were he to press forward.
The Biden administration in April imposed new sanctions on Russia for what it said was Russia's role in the Ukraine conflict as well as allegations that it has abetted cyberattacks on U.S. infrastructure and interference in American elections.
Imposing more sanctions is unlikely to influence Putin's behavior, lawmakers and experts said. The Biden administration in May did waive sanctions related to the Nord Stream 2 pipeline, which will carry Russian natural gas directly to Germany, bypassing Ukraine.
A group of Republican lawmakers this month called on the U.S. to provide more lethal aid to Ukraine's military, ramp up intelligence sharing, or deploy a larger presence of its own to the Black Sea. But Russia could quickly counter with more forces.
And Putin could respond to any Western action by limiting energy exports to Europe, which is heavily dependent on Russian natural gas.
"The traditional tools that nation-states use to govern behavior of other nation-states are not available," said Douglas Wise, a former deputy director of the Defense Intelligence Agency. "The Russians have very little at risk."
Information for this article was contributed by Jim Heintz of The Associated Press.