Ukrainian President Volodymyr Zelenskyy speaks to the US Congress (Image: J. Scott Applewhite/Pool/Sipa USA)

Besieged Ukrainian President Volodymyr Zelenskyy delivered a powerful plea to the US Congress by video on Wednesday, echoing former British prime pinister Winston Churchill’s wartime address to the same chamber and appealing to Americans to recall their own past traumas, from Pearl Harbor to September 11, 2001.

He challenged US President Joe Biden to show more leadership as Ukraine faces an existential fight against an enemy bent on its annihilation.

“You are the leader of the nation … I wish you to be the leader of the world. Being the leader of the world means to be the leader of peace,” Zelenskyy told Biden, after showing a wrenching video that featured images of bloodied children and bodies thrown into ditches.

Zelenskyy received a standing ovation from a packed auditorium of US politicians, many of whom are also demanding that Biden do more. Many of those same individuals also voted to acquit former US president Donald Trump in his first impeachment hearing for short-changing Ukraine of that very same support.

Zelenskyy’s address followed similarly personal, well-tailored appeals to Britain and Canada, in which he invoked Churchill’s famous “We shall never surrender” speech and pleaded with Canadian Prime Minister Justin Trudeau to “imagine you and your children hearing all these severe explosions” if the Ottawa International Airport were bombed.

Zelenskyy’s eloquent pleas highlighted just how tight a geopolitical spot Biden is in right now, one that few if any US presidents have had to navigate.

On one hand, Biden faces a brutal aggressor across the Atlantic Ocean. Russian President Vladimir Putin has all but threatened to start a nuclear war if the US or NATO intervenes directly in Ukraine. On the other hand, Biden finds himself more pressed to help Ukraine in a war broadcast on social media, video and the nightly news, all headlined by the charismatic Zelenskyy, a former TV actor.

Nearly three weeks after Russia’s invasion, Biden has walked that line carefully and, many have said, skilfully, uniting Western allies in announcing unprecedented economic sanctions on Russia and military aid to Ukraine while also assiduously keeping US troops and planes out of the conflict so as not to risk Putin’s wrath. But as political pressure on Biden grows, the line has become fuzzier — and possibly more dangerous.

Further raising the stakes,​​ the prime ministers of Poland, the Czech Republic and Slovenia — three NATO members — travelled to the Ukrainian capital of Kyiv and met with Zelenskyy, risking their own lives to show support for Ukraine. That suggested there could be some cracks within the alliance itself, although NATO secretary-general Jens Stoltenberg reiterated Wednesday that there would not be any no-fly zone in Ukraine, as Biden has said.

White House press secretary Jen Psaki said the same day that Biden was flying to an “extraordinary” NATO summit on March 24 to discuss ongoing deterrence and defence efforts.

“It is fundamentally an unprecedented situation that Biden finds himself in,” said Richard Immerman, a historian and national security expert at Temple University. “Just as in Vietnam we talked about it being the first television war, we now have the first social media war.”

But at the same time, Immerman added, no president has had to figure nuclear Armageddon into his intervention decision-making — at least, not since then-US president Dwight D Eisenhower declined to oppose Moscow’s invasion of Hungary in 1956.

“The nuclear question was never in play in Korea or in Vietnam,” Immerman said.

Following the speech, Senator James Risch, the ranking Republican on the Senate Foreign Relations Committee, called for Biden to “step up and lead”. In a statement, he said: “Let’s send them airplanes, let’s send them air defence systems, and let’s do it faster.”

Democratic Senator Mark Warner, chair of the Senate Intelligence Committee, also demanded more action, saying: “We should heed President Zelenskyy’s call for additional defensive aid including anti-tank weapons and anti-aircraft missiles.”

Zelenskyy called again for Biden to impose a no-fly zone — which could put US pilots in direct confrontation with Russian planes and air defence systems, and which Biden has refused to do.

But he acknowledged that might not happen. “If this is too much to ask, we offer an alternative,” Zelenskyy said. “You know what kind of defence systems we need.”

Biden is under pressure to deliver much more sophisticated surface-to-air missile systems, including former Soviet ones such as S-300s used by some NATO allies, that can reach higher than the Stingers and Javelins already in use. According to CNN, other systems that may already be on their way include Soviet-era SA-8, SA-10, SA-12, and SA-14 mobile air defence systems, which are capable of hitting cruise missiles.

Yet every additional weapons system that comes across the border from NATO countries — especially if they are Russian-made — risks the very sort of escalation Biden has been desperately seeking to avoid.

At her regular news briefing on Tuesday, Psaki was repeatedly challenged on whether Biden’s refusal to allow Russian MiG-29 jets from Poland to be sent to Ukraine by air was very different from what was being sent on the ground. She declined to elaborate on the distinction between them.

Biden spoke to the nation after Zelenskyy on Wednesday, and the administration announced US$800 million in new security assistance in addition to US$200 million announced earlier this week. He also said the US and NATO were working to help Ukraine acquire longer-range missile systems, without being specific, and that he was “committed to surging weapons and equipment” to Ukraine, including 800 anti-aircraft and 9,000 anti-armour systems. But Biden stayed firm on opposing a no-fly zone and the fighter jet transfer.

Psaki sought to stem the tide by noting that Biden was to sign an omnibus bill containing US$13.6 billion in aid and has approved four emergency security assistance packages to provide Ukraine with the types of weapons it is using so effectively to defend the country, such as anti-armour and air defence weapons.

Psaki also said the sanctions on Putin’s oligarch allies in Russia, including the seizure of their yachts abroad, were being stepped up.

Biden’s political quandary is made more pressing by the timid approach of his former boss, former US president Barack Obama, who when Biden was vice-president repeatedly declined to get tough with Putin after his annexation of Crimea in 2014.

The US implemented limited sanctions on Russia — including on its energy, defence and finance sectors — but played down the threat from Moscow.

But most of all, perhaps, Zelenskyy’s eloquence could change the calculus.

In his speech, Zelenskyy called not just for more defence equipment but for sanctions on every Russian politician and official who has not openly disavowed Putin’s invasion. He also implored his congressional audience to close US ports to all Russian goods and ensure that every US company in their districts leave the Russian market immediately. “It is flooded with our blood,” Zelenskyy said.

Biden’s best hope may lie in Ukraine’s mud and Russia’s ineptitude. With the massive invasion bogged down after three weeks of war, even as Russian units close on Kyiv and murder civilians in Mariupol, diplomatic efforts are mounting.

Zelenskyy did not say he wanted to join NATO or the European Union in his address to Congress, a key Russian demand for Moscow to call off its dogs of war.