March 15, 2022, 11:20 p.m. ET

Credit…Brendan Hoffman for The New York Times

President Biden plans to announce $800 million in additional security assistance to Ukraine on Wednesday, White House officials say, just hours after Ukrainian President Volodymyr Zelensky is due to deliver a virtual address to Congress.

Mr. Biden will detail the new military aid in the late morning, shortly after Mr. Zelensky delivers a list of military equipment and other aid he believes is needed to stave off the Russian invasion, including to hold the capital, Kyiv. . . At the top of the list are more anti-aircraft batteries, allowing them to harass – and shoot down – incoming Russian cargo planes and fighter jets around the besieged city.

As well as asking for weapons and warplanes, Mr Zelensky pleaded with NATO to impose a no-fly zone, a move the allies refused because it would put them in direct combat with military forces Russians. To enforce the no-fly zone, US forces would have to eliminate Russian air defenses – inside Russia – and Mr Biden has dismissed that move as unnecessary. Russia has warned it will view a no-fly zone as an act of war.

The administration last week announced $200 million in security assistance for Ukraine. In February, the Biden administration approved a $350 million arms package for Ukraine. In total, the Biden administration authorized $1.2 billion worth of weapons for Ukraine over the past year, officials said.

Those weapons included at least 600 Stinger anti-aircraft missiles and about 2,600 Javelin anti-tank missiles, according to a senior White House official. But what Ukraine needs are more sophisticated anti-missile systems.

So far, the Americans have also supplied Ukraine with five Mi-17 helicopters, three patrol boats and 70 other vehicles of various types.

US aid also includes small arms: 200 grenade launchers, 200 shotguns, 200 machine guns and nearly 40 million rounds, the official said. America also sent one million grenades, mortars and artillery shells, as well as body armor, helmets, tactical gear and military medical equipment, the official said.

The weapons come from existing US military stockpiles in Europe and are flown to neighboring countries, such as Poland and Romania, where they are shipped overland to western Ukraine, the official said.

The Biden administration has also asked Congress for $4.25 billion in new funds for economic and humanitarian aid to Ukrainians.

In addition to weapons, Mr. Zelensky asked Europe and the United States to supply Ukraine with Polish MIG-29 fighter jets. Poland refused to send its aging Russian-made fighters directly to Ukraine, but instead offered to hand them over to the United States, delivering them to a US base in Germany, for ultimate transfer to Ukraine.

The Biden administration rejected this plan because of the risk that it could drag NATO directly into war. Instead, the Biden administration supplied Ukraine with anti-tank and anti-aircraft weapons.