Short of an all-out invasion, Russian President Vladimir Putin could take less dramatic action in Ukraine that would vastly complicate a U.S. and allied response. He might carry out what President Joe Biden called a “minor incursion” — perhaps a cyberattack — leaving the U.S. and Europe divided on the type and severity of economic sanctions to impose on Moscow and ways to increase support for Kyiv.

Biden drew widespread criticism for saying Wednesday that retaliating for Russian aggression in Ukraine would depend on the details. “It’s one thing if it’s a minor incursion and then we end up having a fight about what to do and not do,” he said.

Biden and top administration officials worked Thursday to clean up his comments. Biden stressed that if “any assembled Russian units move across the Ukrainian border, that is an invasion” and it would be met with a “severe and coordinated economic response.”

But even if the “minor incursion” remark was seen as a gaffe, it touched on a potentially problematic issue: While the U.S. and allies agree on a strong response to a Russian invasion, it’s unclear how they would respond to Russian aggression that falls short of that, like a cyberattack or boosted support for pro-Russian separatists fighting in eastern Ukraine.

Ukrainian President Volodymyr Zelenskyy was among those expressing concern about Biden’s “minor incursion” remark.

“We want to remind the great powers that there are no minor incursions and small nations. Just as there are no minor casualties and little grief from the loss of loved ones,” he tweeted.

Complaints came quickly that Biden had made clear to Putin where and how to drive a wedge between the U.S. and its European allies, by using only a portion of the large military force he has assembled near Ukraine’s borders to take limited action. Russian officials have said they have no intention of invading Ukraine, but the deployment of a large combat force along its borders, estimated at 100,000 troops, has created fear of a crippling land war.

“Deeply troubling and dangerous,” Rep. Liz Cheney, a Wyoming Republican and a crucial ally of Democrats on some issues, tweeted about Biden’s remark.

“A greenlight for Putin,” said Republican Rep. Mike Garcia of California, one of many to use that phrase.

Among the possibilities for limited Russian military action: Putin could move much of the Russian ground force away from the border but further bolster the separatists who control the Donbas region of eastern Ukraine. That conflict has killed more than 14,000 people in nearly eight years of fighting.

Biden noted Thursday that “Russia has a long history of using measures other than overt military action to carry out aggression — paramilitary tactics, so-called gray zone attacks and actions by Russian soldiers not wearing Russian uniforms.”

European allies largely have been united with the United States in demanding that Putin not move farther into Ukrainian territory and promising a tough response if he does. But the allies appear not to have united on what political and financial penalties to enact, or even what would trigger a response.

British Prime Minister Boris Johnson said “any kind of incursion into Ukraine on any scale whatever” would be a disaster for Russia and for the world, but he didn’t specify a Western response. Likewise, his defense minister, Ben Wallace, told Parliament, “There is a package of international sanctions ready to go that will make sure that the Russian government is punished if it crosses the line,” but he didn’t define that line, other than warning against “any destabilizing action” by Russia in Ukraine.

Asked Thursday about Biden’s comment on a “minor incursion,” a French diplomat insisted it didn’t prompt any rethinking of the “European consensus” that any new attack on Ukrainian sovereignty would have “massive and severe consequences.” But the diplomat, commenting after meeting with Secretary of State Antony Blinken as he conferred with European counterparts on the Ukraine crisis, wouldn’t elaborate on those consequences or what would constitute such an attack.

The official spoke on the condition of anonymity to discuss his government’s take.

Putin faced limited international consequences after he seized control of Ukraine’s Crimea Peninsula in 2014 and backed the separatist insurgency in eastern Ukraine. His central demand to the West is that NATO provide a guarantee that Ukraine never be allowed to join the alliance — a demand that Washington and its allies have roundly rejected.

Biden on Wednesday noted that coordinating a sanctions strategy is further complicated by the fact that penalties aimed at crippling Russian banking would also have a negative effect on the economies of the United States and Europe.

“And so, I got to make sure everybody is on the same page as we move along,” he said.

Democratic Sen. Jeanne Shaheen of New Hampshire, a senior member of the Senate Foreign Relations Committee and one of the leaders of a bipartisan congressional delegation that visited Ukraine last weekend, said she had seen no signs of a rift with the Europeans over how far Russia would have to go to trigger a response.

In an analysis of the Ukraine crisis, Seth Jones, a political scientist, and Philip Wasielewski, a former CIA paramilitary officer, cited several possible scenarios short of an all-out Russian invasion. This could include Putin sending conventional troops into the Donbas breakaway regions of Donetsk and Luhansk as “peacekeepers” and refusing to withdraw them until peace talks end successfully, they wrote in their analysis last week for the Center for Strategic and International Studies.

“All other options bring major international sanctions and economic hardship and would be counterproductive to the goal of weakening NATO or decoupling the United States from its commitments to European security,” they wrote.

Among those other options: seizing Ukrainian territory as far west as the Dnieper River, which runs south through Kyiv to the Black Sea near the Crimean Peninsula. Putin might seek to use this as a bargaining chip or incorporate this territory fully into the Russian Federation, Jones and Wasielewski wrote.

(AP)