What you need to know:
- To limit Russian air strikes on Kiev and other cities, Ukrainian President Volodymyr Zelensky has begged NATO to establish a no-fly zone over his country. But for now, that is a red line for the transatlantic alliance, of which Ukraine is not a member.
Despite unprecedented sanctions and strong support for Ukraine, Western states have failed to stop the Russian onslaught and are even expecting things to get worse. But their options for intensifying pressure on President Vladimir Putin are likely to be limited.
G7 countries promised Friday to impose "tough new sanctions" on Russia, and the US Secretary of State Antony Blinken pledged to " increase the extraordinary pressure we're already exerting."
But there is not much room for maneuver. The US had promised before the invasion to "start at the top of the escalation ladder and stay there," and have kept their word.
Together with their European allies, they have decreed unprecedented sanctions against the Russian financial system and the oligarchs close to the Kremlin, banned exports of crucial technologies and imposed an air blockade.
Russia has been banned from major sports competitions and dozens of companies have withdrawn from the country.
"Some people thought, and I would be included in this group" that the threat of these sanctions "would be enough to deter President Putin but then it wasn't," former US ambassador to Ukraine William Taylor told AFP.
"And so it's not clear to me that additional sanctions would make him withdraw."
So far, Russia's energy sector has been relatively spared. Many US lawmakers are urging President Joe Biden to ban US imports of Russian oil, something that the president has not ruled out.
Some hawks are also calling for the Russian financial system to be completely cut off from the rest of the world, while Westerners have taken care to target banks that are least linked to the hydrocarbon sector.
Blinken warned against measures that would reduce global energy supply and automatically drive up the price at the pump for Americans and Europeans.
That, he warned, was not in the "strategic interest" of the West, seeming to be betting more on the effect of the current sanctions played out over time.
No fly zone?
To limit Russian air strikes on Kiev and other cities, Ukrainian President Volodymyr Zelensky has begged NATO to establish a no-fly zone over his country. But for now, that is a red line for the transatlantic alliance, of which Ukraine is not a member.
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"The only way to implement a no-fly zone is to send NATO fighter planes into Ukraine's airspace, and then impose that no fly zone by shooting down Russian planes," the alliance's secretary-general Jens Stoltenberg said.
"If we did that, we'll end up with something that could end in a full-fledged war in Europe, involving many more countries and causing much more human suffering. So that's the reason why we make this painful decision."
Raising the specter of nuclear confrontation, many experts think that is why the US and the Europeans will not deviate from this course, as long as the conflict remains confined to Ukraine or any other non-NATO countries.
Inside the Beltway in Washington, a handful of elected Republicans like Adam Kinzinger and Roger Wicker believe, however, that the allies will ultimately have to take the risk of a no-fly zone.
Absent such a solution, Washington and the European Union have for the time being committed to continuing to deliver arms to the Ukrainian forces.
Here, too, voices are being raised in favor of providing more offensive equipment, including Soviet-made fighter planes that some Eastern European countries have and that Ukrainian pilots already know how to handle.
Republican Senator Lindsey Graham did not mince his words: he called on "someone in Russia" to assassinate Putin.
"We are not advocating for killing the leader of a foreign country or regime change," said White House press secretary Jen Psaki. "That is not the policy of the United States."
But some observers believe that by draining the Russian economy and, above all, the assets of the oligarchs who have enriched themselves from their proximity to the Kremlin, the sanctions might push certain members of Putin's inner circle to turn on him.
"The probability of a palace coup or an oligarchic revolt is substantial," said Jean-Baptiste Jeangene Vilmer, director of France's Institute for Strategic Research at the Military Academy in France, in an article for the online site War on the Rocks.
Others, like Samuel Charap of the think tank Rand Corporation, are more skeptical.
"The people who have the ability to affect things are extremely loyal and they are there for their loyalty," he told AFP.
According to Charap, Biden should continue, like French President Emmanuel Macron and German Chancellor Olaf Scholz, to try to convince his Russian counterpart to withdraw, relying on the power of sanctions to prod him onward.
"That might be impossible. But I think that's the best thing we can do right now," he said.
Some are betting instead on another adversary of the United States and the Europeans: China.
One Western diplomat noted that "Beijing is becoming more and more uncomfortable with what's going on" and has not come to the aid of the Russian economy to mitigate the effect of the sanctions.
China can therefore play a much more effective role, behind the scenes, than the West, the diplomat said.