(CNN) President Joe Biden's choices and challenges on Ukraine were already extremely tough. As the war's horror mounts, they are about to get even more excruciating.
Since Russia launched its onslaught last month, Biden has sought to punish and isolate President Vladimir Putin and to mitigate the slaughter of civilians by providing defensive weapons to the Kyiv government. But he's also calibrated his actions to avoid being dragged into a dangerous direct conflict with nuclear-armed Russia while finessing his own delicate political situation at home.
As Putin escalates his assault, Ukrainian President Volodymyr Zelensky gets more desperate and the civilian toll becomes more appalling by the day, Biden's balancing act becomes much harder.
The political heat on the President, after a period of unusual unity in Washington, is also about to rise. That will especially be the case if, as appears increasingly likely, the rest of the world is forced to watch an inhumane Russian siege and bombardment of Kyiv.
In a big Washington moment on Wednesday, Zelensky will deliver a virtual address to Congress. If his recent speech to the UK parliament, which drew Churchillian comparisons, is any guide, it will be a searing and inspiring rallying cry for lawmakers. If the Ukrainian President includes last-ditch pleas for fighter jets and a no-fly zone over his country, which Biden scotched on the grounds they could trigger war with Moscow, he will create extreme domestic pressure on the President.
Biden's problem is that after unleashing full-bore economic warfare on Russia with extraordinarily tough sanctions, there are now limits to the steps he can take to significantly turn up pressure on Putin without risking a direct military or cyber conflict. Some of the President's critics in Congress and in parts of the foreign policy establishment, including in his own party, argue that he's been too cautious.
But it's one thing for a lawmaker to accuse Biden of bowing to Putin's threats. A President has profound responsibilities in a situation like this and cannot risk miscalculations. The White House has been exceedingly careful not to push a vengeful and increasingly reckless Putin into even more of a corner. It, for instance, did not respond in kind to his order last month to put his nuclear forces on higher alert, and interpreted the Russian leader's atomic poker as an attempt to intimidate the West. In the same vein, Pentagon spokesman John Kirby on Monday declined to describe a Russian air strike on a Ukrainian base close to the Polish border as a new phase of the conflict that could threaten NATO territory. The administration is determined to avoid giving Putin an excuse for the conflict to spill over Ukraine's borders.
But Biden is still the first commander in chief since the 1980s who has to navigate the genuine possibility of an escalatory cycle with Moscow that could risk a nuclear war. He must also consider how he would respond if a Russian missile strayed onto NATO territory in eastern Europe -- a scenario that, in theory at least, could trigger the alliance's Article Five collective defense clause.
Biden, who came to Washington as a young senator at the height of the showdown with the Soviet Union, now faces the same lonely burden of Cold War presidents -- the fate of the world may be on his shoulders. And the situation may be fraught with more uncertainty than in the long decades of the Soviet-US standoff. The doctrine of mutually assured destruction, which underpins the notion of nuclear deterrence, held throughout the Cold War. The question is now being asked whether Putin, humiliated and with his political survival on the line, would maintain the same red lines as his Communist predecessors.
"The prospect of nuclear conflict, once unthinkable, is now back within the realm of possibility," UN Secretary-General António Guterres said Monday, referring to Putin's raising of his country's nuclear alert as "bone chilling."
A senior US official, speaking after intensive talks with China on Monday that focused partly on Ukraine, put it this way: "There's a lot of gravity in this moment." It's no wonder, as CNN's Kevin Liptak reported earlier this month, that senior officials believe the Ukraine crisis will largely define Biden's term. Sources also said Monday that the President was considering a visit to Europe -- a trip to bolster NATO morale that would immediately become the most critical journey across the Atlantic by any American president in decades. The leaders of NATO could meet in person in Brussels as soon as next week, a diplomatic source familiar with the planning told CNN's Kaitlan Collins Monday evening.
If the strategic stakes were not high enough, the huge importance of the President's next moves is being exacerbated by the failure of an international diplomatic effort to get Putin to climb down and Russia-Ukrainian talks that have yielded no breakthroughs.
The Russian President has turned his country into an economic, diplomatic, cultural and sporting pariah. Russia has been embarrassed about the slow advance of his forces, after earlier predictions of a Blitzkrieg and heroic resistance of Ukrainians. But everything the world has learned in Putin's more than two-decades in power about his psychology and his track record suggests his instinct will be to intensify the war. A weekend of vicious attacks on civilian targets like apartment blocks and bombardments and sieges of multiple cities suggest this is already happening.
"If Ukraine will not bend the knee to Russia, he will make sure that Ukraine is going to be a wasteland," Heather Conley, the president of the German Marshall Fund, said on CNN's "Inside Politics" on Monday.
Retired Brig. Gen. Mark Kimmitt said on CNN "Newsroom" on Monday that Putin's tactics, which have already drawn accusations of war crimes, are about to get even more extreme.
"Now that they have realized that this is a slog, they are doing what they have always done in history, which is a slow bulldozer-like vehicle that pushes everything out of their way or underneath them. They are going to start the siege of Kyiv pretty soon, and I think we will see that strategy play out," Kimmitt said.
Pictures emerging from the besieged coastal city of Mariupol, which has been devastated by Russian bombardments and where there is little heat, electricity or food and water, and from villages outside of Kyiv offer a frightening vision of what may lie in store for the capital.
The spectacle of a prolonged Russian siege of Kyiv, with mass civilian casualties and unfathomable destruction, would leave Biden vulnerable to charges that he was not intervening to prevent a genocide or war crimes. It would impose extraordinary global and domestic political pressure on the President to overcome his reticence to employing measures that could risk a direct US-Russia conflict.
Biden, who came to power stressing his empathy and compassion in the middle of a pandemic, might eventually be the President at the other end of the phone line, having to explain to Zelensky why the West could not do more to save Ukraine.
Signs that the battle for Kyiv could be looming added fresh urgency on Monday to calls in the US Congress for Biden to do more, as it emerged Zelensky would address a Joint Session by video link on Wednesday. The Ukrainian President's courage has helped inspire the Western world to unite and punish Putin in far more robust terms than many expected. The alliance is again in the business of killing Russian soldiers after launching what is effectively a proxy war in Ukraine by providing anti-aircraft and anti-tank missiles. So far, those measures have not prompted Putin to turn directly against the West, though Russia has warned it sees such shipments as legitimate targets.
That has encouraged Biden critics in Congress to warn that Washington's opposition to Poland's offer to send Soviet-era jets to Ukraine amounted to the US bowing to a Russian bluff. Only a few members of Congress have called for a no-fly zone over Ukraine, underscoring reluctance to send US service personnel into harm's way and into an alarming head-to-head clash with Russia. But Senate Republican Whip John Thune said Monday there is broad bipartisan support for including a provision approving the deployment of military aircraft to Ukraine in a bill targeting Russia's energy imports and trade status.
"I know the administration has its position on that. But there would be a lot of bipartisan support for jets," Thune, of South Dakota, told reporters on Monday.
Nevada Democratic Sen. Jacky Rosen, who sits on the Armed Services Committee, has called on the administration to help Ukraine get more warplanes.
"The President is still resistant," Rosen told CNN's Jake Tapper on Monday, referring to the Polish jets plan. "I think they are continuing to work with our NATO allies trying to find a back channel without provoking World War III."
Her comment encapsulated the dilemma that Biden faces in navigating a path through the conflict that does everything the US and its allies can do to stave off a humanitarian outrage while containing the war inside Ukraine. But the crisis is approaching a point where doing both will become increasingly challenging.