U.S. President Joe Biden promoted the importance of U.S. and allied weapons for Ukraine’s defense on Tuesday during a visit to a Lockheed Martin Corp. plant making Javelin anti-tank missiles, which American and NATO officials say have mauled Russia’s invading armored columns.

Biden’s trip to the Troy, Alabama, factory comes as the president is pushing lawmakers to authorize an additional $33 billion in aid for Ukraine — and as lawmakers warn that stockpiles of the U.S. Army and Marine Corps’ premier anti-tank weapon are becoming depleted due to the war.

The self-guided portable missile system — which weighs just 49 pounds (22 kilograms) — has proved invaluable to Ukrainian fighters, who can fire on Russian vehicles from as far as 4,000 meters (2.5 miles) away and then quickly flee. The U.S. has already delivered about 5,000 of the 5,500 Javelins the White House has committed to provide to Ukraine, a senior defense official told reporters Monday.