WASHINGTON, United States (AFP)— Ukraine’s leader Volodymyr Zelensky made a desperate appeal for help against Russia to the US Congress on Wednesday, and within hours of the speech, President Joe Biden responded by promising $1 billion in new weapons to fight “war criminal” Vladimir Putin’s invading army.

The Ukrainian president’s video address from embattled Kyiv, bolstered by a montage of horrific TV footage of Ukrainian civilians under Russian assault, delivered an emotional gut-punch to US lawmakers.

Bearded and dressed in a military green T-shirt, the Ukrainian leader invoked September 11 and Pearl Harbor as he pleaded again for a Western-enforced no-fly zone to bar Russian warplanes, something Biden has rejected as almost certainly leading to what he says would be “World War III.”

More than three weeks into a war that has claimed hundreds of civilian lives and turned more than three million Ukrainians into refugees, Zelensky said his country was battling “a terror that Europe has not seen… for 80 years.”

“Remember Pearl Harbor, terrible morning of December 7, 1941, when your sky was black from the planes attacking you,” he said, recalling the air raid that brought the United States into World War II.

“Protect our sky,” he said.

But in a nod to Western concerns, Zelensky added that an alternative to the no-fly zone would be more powerful weapons to allow Ukrainians to defend themselves.

Just hours later, Biden delivered his response: an extra $800 million in military aid, which added to another installment last week brings the latest deliveries to $1 billion — and $2 billion since Biden took office.

The new batch includes 800 Stinger anti-aircraft systems, thousands of anti-tank weapons including 2,000 of the now-famously deadly Javelin rockets, 100 “tactical” drones, 20 million rounds of small arms ammunition and 25,000 sets of helmets and body armor.

Ukraine has already been given hundreds of Stingers, which can shoot down relatively low flying aircraft.

But Biden said that “at the request of President Zelensky, we have identified and are helping Ukraine acquire additional longer-range anti-aircraft systems.”

A US military source, who spoke on condition of anonymity, said the weapons system under discussion was the S-300, a sophisticated missile that is of Russian design but owned by some European NATO members and seen as easy to integrate into Ukraine’s military.

The drones mentioned by Biden are a US weapon called Switchblade, which has the ability to loiter over a target, before plunging down like a bomb, the military source said.